Too pleasure one's self in a sexual way
T: dude i was jackin it major last night!
Jackin it - The slang term for masturbate
–verb (used without object)
1. to engage in masturbation.
–verb (used with object)
2. to practice masturbation upon.
Origin: 1855–60; < L masturbātus, ptp. of masturbārī to engage in masturbation
Dictionary.com Unabridged (v 1.1)
You: Where is Nick?
Me: Oh, he is at his house jackin it to some porn.