n.1 colloq. a foolish person.
2 Brit. the thick end, esp. of a loin of lamb or mutton (chump chop).
3 a short thick block of wood.
4 Brit. sl. the head.
Phrases and idioms:
off one's chump Brit. sl. crazy.
Etymology: 18th c.: blend of CHUNK and LUMP(1)