(intransitive) To preemptively raise ad hominem arguments in order to discredit someone. / Used other than figuratively or idiomatically: see poison, the, well.

(Australian rules football, humorous) A fictitious disease said to be contracted by a player who accumulates a large number of possessions of the ball.

(idiomatic) Something which is initially regarded as advantageous but which is later recognized to be disadvantageous or harmful; an apparently beneficial or benign instrument or scheme for causing death or harm.

plural of poison ivy

plural of poisoned chalice

A woody shrub or small tree, all parts of which cause irritation to humans; Toxicodendron vernix, formerly Rhus vernix.

plural of poison sumac

A poisonous gas. / (military) Any poisonous gas used as a chemical weapon.

plural of poisoned pawn

(chess) An unprotected pawn whose capture would be a losing move for the capturing player.