Green’s Dictionary of Slang

munch v.1

1. [17C; 19C; 1980s+] to eat, esp. enthusiastically; thus munching n. and adj.

2. [1960s+] (also munch the box) to perform oral sex.

3. [1980s] (US campus) to kiss.

In compounds

munching house (n.)

[1910s+] a cheap restaurant or café.

munch-present (n.) [he fig. ‘eats’ the money]

[mid-16C–early 17C] one who takes bribes.

In phrases

munching the truncheon (n.) [truncheon n.]

[1990s+] fellatio.

munch out (v.)

1. [1970s+] (orig. US campus) to eat voraciously, esp. as a result of smoking cannabis.

2. [1980s+] (US campus) to kiss passionately.

munch the box (v.)

see sense 2 above.

munch the trunch (v.) [truncheon n.]

[1990s+] (UK juv.) to fellate.