jam-up I. \ˈ ̷ ̷ˌ ̷ ̷\adjective Etymology: probably from jam up, v. : very good : first-rate : bang-up < after one course in psychology you turn out to be a whiz-bang, jam-up mind reader — J.S.Redding > II. noun (-s) Etymology: from jam up, v. : jam II 1