Green’s Dictionary of Slang

1. a rumbustious, uninhibited party.

1984

Partridge DSUE (8th edn) 1222: [...] since late 1930s.

2. a drinking spree.

1967		J. Wynnum I’m a Jack, All Right 40: That only applies once every pancake day when all the station hands head in to town for a bit of a thrash.
2003		C. Jones posting 24 May at JobintheSun.com 🌐 CI$5.50 a pint is pretty steep!!! I wouldn’t be able to go on a thrash too often!!!

3. any form of fast, loud and harsh-sounding music; also attrib.

1988		G. Tate ‘Public Enemy’ in Flyboy in the Buttermilk (1992) 127: Got to say, though, the thrash is deadly.
2002		Guardian 22 Feb. 🌐 This is the peculiar world of Slipknot, the brutal US thrash metal ensemble who are now – by no small margin – the most extraordinary rock band around.