Define ambush. ambush synonyms, ambush pronunciation, ambush translation, English dictionary definition of ambush. n. 1. A sudden attack made from a concealed position. 2. a. Those hiding in order to attack by surprise: The captain stationed an ambush near the harbor. Ambush | Definition of Ambush by Merriam-Webster Ambush definition is - to attack by surprise from a hidden place : waylay. How to use ambush in a sentence.