Entry 3 senses · 2 variants Webster, 1913 lumpen · lump·en · IPA /ˈlʌmpən/ adj. n. 01 adj. mentally sluggish. 1. mentally sluggish. Syn. lumpish, sluggish, unthinking. 02 n. same as lumpenproletariat. 1. same as lumpenproletariat.(Politics) See: lumpenproletariat 2. The European eelpout; -- called also lumper.(Zool.) Also: lumper