From Wiktionary, the free dictionary
Somehow related to pum-pum.
poomplex (plural poomplexes)
- (Jamaica, MLE, slang) A weak or worthless man.
2006 December 13, “R U Dumb?”, in Jme (lyrics), Boy Better Know - Edition 2: Poomplex[1], 0:57:Shh hut yuh muh
Derkhead, wasteman, poomplex