Noun: stimulation of the privates through one's trousers, hand-to-jeans frottage, a masturbatory dry hump. Conjunction of "trouser" and "wank".
"My boss got tranked off in a bar" or "Those lapdancers give you a bit of a butt trank".
A cumshot
Piers: hey Phoebe do you want a trank
Phoebe: yes please it sounds fun