Green’s Dictionary of Slang

1. (US) an erection [the shape; in (2) it is inhaled from a balloon].

1998

D. Jenkins Rude Behavior 33: ‘This hard-on showed up, Claude. It was a big-time bulb, a fucking blue veiner, man’.

2. (UK gang) nitrous oxide.

2018-20

T. Thorne (ed.) ‘Drill Slang Glossary’ at Forensic Linguistic Databank 🌐 Bulb – nitrous oxide.

3. (Irish/Cork) one who looks like, a twin of.

2015		L. McInerney Glorious Heresies 163: ‘He’s the bulb off you. It’s unreal. Are you trying to tell me you’re not Ryan’s dad?’.
2021		L. McInerney Rules of Revelation 167: ‘Diarmaid. Lovely name. He’s the bulb off you’.