wack (2)EnglishOxford New American Dictionarywack2 /wak, wæk / informal, mainly US ▸ adjective bad; inferior: a wack radio station. ▸ noun 1 a crazy or eccentric person: the kids were learning to live with the idea that Dad was a wack. 2 worthless or stupid ideas, work, or talk; rubbish: this track is a load of wack. – ORIGIN 1930s : probably a back-formation from wacky.