Green’s Dictionary of Slang

1. the act of copulation.

1725

‘When My Dimber Dell I Courted’ in Farmer Musa Pedestris (1896) 48: Wanton joys my heart transported, / And her wap was ever new.

2. (UK Black, also whapper) a gun.

2016		1011 ‘Next Up?’ 🎵 Took you 20 shank wounds, now you’re only bringing waps?
2017		67 ‘Waps’ 🎵 Them opp boys just run their mouth, they don’t know nuttin’ about waps.
2017		1011 ‘No Hook’ 🎵 My bro’s them been crashing corn / I don't know for these so called crashers / Got hands on whappers.
2020		G. Krauze What They Was 223: I need to get that three bags [...] and I need the wap.

3. see wop n.¹ (1)