what a ball has after it roquets another ball. It becomes "dead" on that ball and cannot roquet it again until it scores a wicket to become "alive" or becomes "alive" on it after clearing under the 1-back rule.

the physical property of something that has lost its elasticity; "he objected to the deadness of the tennis balls"

This is the ineligibility to earn bonus strokes when you've hit another ball with your ball.

ineligibility to earn bonus strokes by hitting another ball with your own ball.

When a strikers ball hits another ball, the striker cannot use that ball until going through the next wicket. The striker is dead on the other ball, after taking the croquet shot.