Green’s Dictionary of Slang

1. to molest a child.

1994		I. Welsh ‘The Shooter’ in Acid House 8: The cunt beasted little Lisa [...] made her go down on him.
2012		(con. 1980s) I. Welsh Skagboys 49: Gilbert O’Sullivan wrote that fuckin nonce song aboot beastin bairns.

2. to subject to physical abuse, thus n. beasting.

2004		B. Parris Making of a Legionnaire 158: [O]ur usual beasting—running along being shouted at, cursed at and generally abused .
2005		Guardian 25 Jan. 🌐 Maj Taylor has denied that he ordered the captives to be ‘beasted’, ‘thrashed’ and forced to run for three miles.
2018		Guardian 2 Jan. CiF 🌐 National service. [L]et the military beast the fuck out of them [i.e. knife-carrying youth].
2018		J.-P. Jordan Joys of War 44: Beastings is the endearing term for gruelling and punishing physical training [...] Anything to push you to your limit and beyond, physically and mentally.