A new method off masturbation, generally employed by middle aged men who have got bored of the conventional method.
It simply involves rubbing ones "ball sack" until ejaculation. By acheiving orgasm through merely rubbing ones balls, you can be described as "sacking off" as opposed to the more usual "jacking off".
Clearly can be used in many tenses, and as a verb, noun and adjective;
I, he, she is going to sack off tonight.
I, he, she sacked off last night.
I, he, she had a really good sack off last night.
I, he, she is a total sacker offer.
"I'm going to go home, open a bud, put on MTV2 and have a good sack off to the Pussycat Dolls video".
"Stop talking shit, you sacker off"
"You're a real sack off"
"Last night was amazing, my girlfriend came round for the annual blowjob and steak day (March 20th - google it!!), but she surprised me at dinner by sticking her hands down my pants and giving me the most amazing sacking off"