Green’s Dictionary of Slang

rat fuck v.

[rat fuck n.2 (1)]
(US, mainly campus)

1. (also r.f.) to play a practical joke on someone, to outwit, to trick.

[US]Current Sl. II:1 6: RF, v. To play a dirty joke on someone.
HairyMary on Urban Dict. 🌐 rat fuck to screw someone ova in a vengance. He cut my brake lines and rat fucked me as i went down the hill into traffic.

2. to break off a relationship.

[US]P. Munro Sl. U.

3. (N.Z./US) to cause (serious) problems for; spec. to inform against.

R.L. Ruiz Happy Birthday Jesus 34: If you guys want to rat fuck him, then do it.
[NZ]McGill Reed Dict. of N.Z. Sl. 170: ratfuck Cause excessive harm, eg, ‘Drug dealers often ratfuck each other, not just on deals but even enticing rivals into boobytrapped marijuana plantations.’ 1990s.
[US]Simon & Burns ‘Bomb in the Garden’ Generation Kill ep. 7 [TV script] Respectfully, you’re asked to ratfuck some other establishment.
[US]C. Hiaasen Squeeze Me 62: ‘The feds cut your time ’cause you flipped. You rat-fucked your friends’.
[Aus]C. Hammer Opal Country 445: ‘I am in the process of completely ratfucking Bullshit Bob Inglis’.

4. to rummage, to search.

[US]G. Pelecanos Way Home (2009) 201: The trunk opened, and Ben could hear Wayne ratfucking through it.