Green’s Dictionary of Slang

(US prison) to perform anal rape.

1986		C. Stroud Close Pursuit (1988) 95: Good looks had been a problem in Rikers, getting him ‘maytagged’ at least eight times before he got old enough and fast enough to cause some pain in the process.
1989		J. Morton Lowspeak 97: Maytag – to commit the act of homosexual rape.