Verb, meaning to take semen from a man against his will. Typically this will be done by a pre/early-thirties woman to her soon to be ex in order to secure a set of fertilised eggs for later implantation, although it could also have uses in framing someone for crimes with a sexual angle.
The origins of the term come from a discussion surrounding a recent case in ireland in which a man blocked his ex-wife's attempts to have eggs which he had fertilized implanted in order to bear children. His arguement was that half the genetic material was his. However, unless said material was taken by force, he must have willingly donated it, there by creating a 'gift' of his sperm. So for his case to hold water, only one thing could have happened - he'd been spunkjacked. (Had he won the case, he could have said to have had spunk justice)
Interestingly there is no antonym since you can't put it back in once it's out. To date, I am unaware of any cases in which anyone has tried to force one mans semen into anothers Japs eye but if it happens to you then please accept my sincere condolences.
Contrary to popular belief, Spunkjacking is not a victimless crime. At least 2 million of the little white soldiers stand to die in a failed hit. And most men do not appreciate getting a hand job if you don't wake them up when it's happening.
Luckily, you can help cut down on Spunkjacking in your area. When a woman gives you a mouth-based treat, make sure you donkey punch her so she is forced to swallow. Also, having a spare condom or even an empty crisp packet handy can be a life saver.
So she's all like, sucking my cock but I never checked that that bitch had swallowed, next thing I know I have a paternity suit on my hands. She's a god damned Spunkjacker!
But officer, I've never even seen this dead woman before. How could my semen be all over her face, hands and clothing? Dear God! I've been Spunkjacked!