"exting" or "ex-ting" is when you get stupidly drunk and start texting your ex girlfriend or boyfriend because it seems like the best idea in the world.
Jo: Yo, i'm hooking up with Kim this weekend!
Rob: Dude, Kim's a hot bitch, plus you guys broke up like 3 months ago...
Jo: I know, but i was exting her on friday and she said she has some new sex positions.