Dummy/ˈdʌmi/ Definition 1 of 5Pro Tip 1/2Retail Display Used to refer to mannequins in stores showing how clothes look when worn. The designer arranged several dummies for the new collection's showcase. Pro Tip 2/2Safety Testing 'Dummy' often refers to the mannequins used in safety tests, like car crashes. Crash test dummies help car manufacturers improve safety features.