An ejaculation so powerful, it can't be held back and explodes across the room. Or in the case of a blowjob, causes the blower to gag a little from the sudden blast at the uvula, and leaking. During intercourse, it gushes out from the openings. Also known to break condoms.
Jack: Dude.... That girl sure knew how to blow....
Jason: Say wha...?
Jack: It was so good, I had an ejacusplosion and she almost choked!
Jason: DAMN! O_o
John: Dude... I'm in trouble...
John: I... may have gotten Jessica pregnant?
Frank: WTF! Why didn't your dumbass use a condom?!
John: I did.... My ejacusplosion blew a hole in the tip...
Frank: ._. ....