Green’s Dictionary of Slang

twat v.

[twat n. (3)]

1. to hit someone.

[UK]A. Sayle Train to Hell 126: Then she twatted me on the head with the cash register.
[UK]Indep. on Sun. Culture 11 Oct. 9: With their perpetual drunkenness, big arms, and talk of twatting poofs.
[UK]A. Guthrie Hard Man 214: I twatted him a beauty.
Twitter 27 Jan. [Internet] 2016: ‘The NHS will be up to its fucking tits in money.’ 2019: ‘You’ll be twatted in the back of your stupid fucking head with the butt of a military grade assault rifle if you dare to leave your soon-to-be-repossessed house’.

2. to behave in an unsophisticated manner.

[UK]Guardian Guide 15–21 May 25: The two dizzy sorts [...] twatting about in service station sunglasses.

3. to waste time.

[US]Hip-Hop Connection Jan.–Feb. 35: So don’t twat about.

In phrases

twat on (v.)

to talk inconsequentially, to chatter.

[UK]N. Blincoe ‘Ardwick Green’ in Champion Disco Biscuits (1997) 3: So far, the kid hadn’t stopped twatting on about his idea for a perfect Sunday afternoon.