Leo Postma assassin as⋅sas⋅sin [uh-sas-in] –noun 1. a murderer, esp. one who kills a politically prominent person for fanatical or monetary reasons. 2. (initial capital letter) one of an order of Muslim fanatics, active in Persia and Syria from about 1090 to 1272, whose chief object was to assassinate Crusaders a home a b c d e f g h i j k l m n o p q r s t u v w x y z ascent asleep assassin astray atmosphere autumn avert away