Green’s Dictionary of Slang

1. (orig. Aus./N.Z.) to overwork a piece of machinery, e.g. an automobile; thus thrashing n.

1997		N. Barlay Curvy Lovebox 157: Thrash it down Ladbroke Grove hard as I can.
2002		M. Cryer Curious Kiwi Words 217: This thrashing of the non-human [...] can involve such a vehicle as a tractor or a car being given a thrashing – being used relentlessly or at high speed.

2. (US campus) to wreck, to make a mess of.

1981		J. Ellroy Brown’s Requiem 108: Somebody righteously thrashed old Omar’s pad the other day.
1989		P. Munro Sl. U.
1997		E. Little Another Day in Paradise 226: The last week of shooting dope has thrashed him, too.