vap, n. — Green’s Dictionary of Slang

vap n.

[? Fr. vapeur, dizziness, light-headedness + obs. SE the vapours]

(W.I./UK black)

1. a bad mood.

1996

2. an impulse.

1956		S. Selvon Lonely Londoners 53: Who can tell what was the vap that hit Cap and made him get married?
1957		S. Selvon Ways of Sunlight 127: This was not the first time Mangohead get vap to create calypso.

catch a vap (v.) (also ...vapse)

(W.I.) to be suddenly inspired to do something, to do something on the spur of the moment.

1996