The Collaborative International Dictionary of English v.0.48:
Dumps \Dumps\ (d[u^]mps), n. pl. a gloomy mental state; same as 2nd dump[1]; -- used mostly in the phrase "in the dumps". [PJC]WordNet (r) 3.0 (2006):
dumps n 1: an informal expression for a mildly depressed state; "in the dumps"; "have the mopes" [syn: dumps, mopes]