Accuracy X/-X: A cumulative, static ability that means, "Add X to each of this unit’s attack dice." and "Subtract X from each of this unit’s attack dice." respectively. Accuracy can’t alter "natural" rolls to affect Critical Hit, Fury, or Parry, but it can affect your chance against Armor. If a unit gets the Accuracy ability after you roll attack dice, it's too late to affect the hits.
Alternative Cost
Alternative Cost: [cost]: A selective, static effect that means, "Instead of paying the build cost of this card, you may complete this card by paying the [cost] listed." Alternative Cost must be paid in full, if it is not possible to pay the [cost] completely, you can't complete the card. You must pay the [cost] in the order listed. Any ability that reduces the normal cost to complete a card does not reduce the [cost] in that card's Alternative Cost, unless the ability specifically says so.
Armor
Armor: An isolated, static ability that means, "This unit can only be hit on a roll of 5 or more." Armor works against dice of damage and attack dice. It redefines what die roll is required to hit a unit. It doesn’t modify the die roll like Accuracy. A unit with Accuracy 1 attacking a unit with Armor hits with 4's, 5's, and 6's.
Backfire
Backfire X: A cumulative ability triggered by the initial dice roll that means, "When you roll at least one natural three with this unit's attack dice before re-roll, this unit does X dice of damage to itself when the attack ends." Backfire applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.
Bombard
Bombard X: A cumulative, static ability that means, "This unit may attack a unit in the Ground arena instead of the Space arena, using X power plus any other effects." You choose whether to use Bombard to attack a unit in the Ground arena or to make a normal attack in the Space arena. You can't attack a unit in the Space arena using Bombard. Power changes affect Bombard.
Critical Hit
Critical Hit X: A cumulative ability triggered during the pending damage POP that means, "If you rolled at least one natural six with this unit's attack dice, this unit does X more damage for this attack." Only one natural "6" counts in the attack roll after re-rolls. If a unit gets the Critical Hit ability after you roll attack dice, it's too late to affect the damage. Accuracy can't increase the die roll to a natural "6". However, you or your opponent may use an effect to re-roll dice to affect the number of natural sixes. (You only count the six, if any, from the roll used for the attack.) Critical Hit applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.
Damage Control
Damage Control X: A cumulative, triggered ability that means, "When your build step starts, you may remove up to X damage counters from this unit."
Double Damage
Double Damage: An isolated, static ability played during the damage placement POP that means, "Put 1 additional damage counter on the defending unit for each 1 damage that wasn't prevented." Damage counters placed by a unit with Double Damage are in addition to the counters that would be placed normally if the attacking unit did not have Double Damage.
Double Strike
Double Strike: An isolated, static ability played after the attack end POP that means, "You may choose a unit that this unit can attack. This unit attacks that unit. Play only if this unit just attacked and only if it tapped for that attack." The unit must tap for the first attack, not the second. If it untaps, it may double strike again. Double Strike doesn't allow you to attack your own units.
Elude
Elude: An isolated, static ability that means, "This unit cannot be intercepted." An attacking unit with Elude cannot have the target of its attack changed by a unit with the Intercept ability. The "Elude" Keyword has been renamed to "Precision". Treat any unit with Elude as if it has Precision instead.
Evade
Evade X: A layered ability activated during the damage prevention POP that means, "Prevent up to X damage to this unit." You can play Evade only once for each instance of damage. You don't have to use all of the Evade. You choose how much damage to Evade up to X, even if the full amount of damage or more is pending.
Lucky
Lucky X: A cumulative, static ability that means, "Each time this unit attacks or is attacked, you may re-roll up to X of this unit's attack dice or have your opponent re-roll up to X attack dice against this unit." Both players can use Lucky effects according to the rules for POP chances. Lucky is used only once after all triggered re-roll effects resolve. You can't re-roll more dice than are rolled for the attack. You may choose to roll any number of dice up to the Lucky value.
Overkill
Overkill: An isolated ability triggered during the pending damage POP that means, "When this unit attacks, you may divide hits in excess of the defending unit's remaining health between that unit and another unit in the same arena." The player who controls the attacking unit decides how many hits (if any) in excess of the defending unit's remaining health to reassign as damage to the second unit. (That player can't change their mind afterward.) A number of hits equal to the defending unit's health must be assigned to the defending unit, and the remainder may be assigned to the defending unit or another unit in the same arena. Overkill damage is caused by the ability, not the die roll. Shields, Parry, and Armor have no effect against it, but damage prevention not specifying dice works normally. Both units resolve damage in tandem.
Parry
Parry X: A cumulative ability triggered during the damage prevention POP that means, "If the attacking unit rolled at least one natural '1' against this unit, prevent X damage to this unit." Only one natural "1" is counted from the attack roll after re-rolls. Parry doesn't prevent damage from a parrying unit unless it attacks itself. Parry can't affect unpreventable damage. If a unit gets the Parry ability after you roll attack dice, it's too late to affect the damage. Accuracy can't decrease the die roll to a natural "1". However, you or your opponent may use an effect to re-roll dice to affect the number of natural ones. (You only count the 1, if any, from the roll used for the attack.) Parry applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.
Pilot
[sub-type] Pilot: A layered, static ability written as "[sub-type] Pilot. The [sub-type] gets:… ." that means, "You may move this card onto or off of a non-Droid Space or Ground unit of the correct sub-type once during the build step. Ignore all other text on this card except its name, sub-type and health. The piloted unit can't have more than one Pilot." Treat all of a unit's Pilot abilities for a sub-type as a single Pilot ability for that sub-type. It grants abilities to that unit alone. See the "Pilots" section of the rules PDF for more info.
Precision
Precision: An isolated, static ability that means, "This unit cannot be intercepted." An attacking unit with Precision cannot have the target of its attack changed by a unit with the Intercept ability. "Elude" is the former name of this keyword. Treat any unit with Elude as if it has Precision instead.
Reserves
Reserves: [Ability]: A layered, static ability that means, "The following ability works while, and only while, it's in the build zone." The granted ability remains to be the ability of its type. (For example, activated abilities granted by Reserves may be disrupted.)
Shields
Shields X: A cumulative, static ability that means, "The attacking unit gets –X power against this unit." Shields only matters when attack dice are rolled. If you give a unit Shields after your opponent has rolled for damage, it doesn't affect the roll.