Entry 2 senses · 2 variants Webster, 1913 Lu /(lū)/ · IPA /luː/ n. & v. t. n. 01 n. & v. t. See Loo. 1. See Loo. See: Loo 02 n. The chemical symbol for lutetium. 1. The chemical symbol for lutetium.(Chem.) See: lutetium