Green’s Dictionary of Slang

bazooka n.1

[all f. the anti-tank rocket launcher, first used in WWII; like bazoo n.1 the term may stem f. the Du. bazu(in), a trumpet, in this case f. the shape ]

1. a metaphorical part of the body.

[UK]Wodehouse Psmith in the City (1993) 114: Had he not unfortunately dislocated the radius bone of his bazooka while training.
[UK] (ref. to 1930s) R. Barnes Coronation Cups and Jam Jars 106: Oh, doctor, Come at once, / The hen she’s on her back. / She’s twisted her bazooker / And cannot get it back.

2. the buttocks; in up the bazooka

3. the head, the mind, with implications of stupidity.

[UK]Wodehouse Jeeves and the Feudal Spirit 125: Try that one on your bazooka, my dear Cheesewright.

4. the penis.

[Ire]C. Brown Down All the Days 155: And would you kindly take your eyes off my bazooka?
[Aus]B. Humphries Traveller’s Tool 107: The occasional little stewardess who has rashly settled for a bottom-of-the-range Cartier watch and a Bedouin bazooka up her back bottie.

5. (US black) an especially large and potent marijuana cigarette, laced with cocaine [note basuco n.].

[US]ONDCP Street Terms 2: Bazooka — [...] crack and tobacco combined in a joint.

6. (drugs) cocaine, crack cocaine.

[US]ONDCP Street Terms 2: Bazooka — Cocaine; crack.
[Aus]P. Temple Truth 291: On any Friday, an army of couriers hand-delivered snort, bazooka [...] to bankers, brokers, lawyers, accountants [etc.].

7. (US drugs) a cigarette that mixes coca paste and tobacco.

Morn. Call (Allentown, PA) 24 May 38/1: ‘Bazooka’ — joint laced with coca paste.
[US]ONDCP Street Terms 2: Bazooka — [...] coca paste and marijuana.

In phrases

up the bazooka (adv.) [i.e. fig. excrement]

(US) a general intensifier, blatantly, excessively, totally, reprehensibly, in large quantities.

[US]Eble Campus Sl. Fall 6: out the ass – in large quantities: I have mid-terms out the ass this week. Also up the shit, out the butt, up the bazooka.