Any pawn that, if captured, would lead to serious disadvantage is considered to be poisoned.

A Pawn (often White's Pawn on b2) which is undefended during the opening but which if taken, often permits the player who gave up the Pawn to engage in a strong attack or to later win the piece taking the Pawn.

Any pawn that appears to be free for the taking but which will set off a trap against you if you do.