Green’s Dictionary of Slang

1. defeated comprehensively, broken, destroyed.

2000		Anita Letters at Quandaryland.com 27 Apr. 🌐 I am a firm believer in the fact that you don’t have to walk into a room and instantly get mullered to be playing a good game and using initiative and objects is more important for overcoming obstacles than blowing someone’s head off at just the right time.
2003		‘Boat Buoys’ Diary’ on ‘Scrapheap’ Channel4.com 🌐 [He] stupidly drove into it. Buoy, rope, chain and finally anchor were all sucked up by the great oil-drum screw, and [...] it was only a short time left before that drive-shaft really got mullahed, leaving us to win again.

2. drunk, absolutely intoxicated.

2000		BBC.co.uk 7 Jul. 🌐 Meanwhile, under the headline ‘Blair o’ the dog’, the Daily Star urges: ‘Don’t be too hard on Euan. Didn’t YOU ever get mullahed when you were a kid?’.
2005		P. Howard Curious Incident of the Dog in the Nightdress 2: My marriage has just broken up. Think that entitles me to get mullered.