The title given to any person with the uncanny knack for accidentally interrupting folks having sex, generally right before they climax. The type of interruption can range from a phone call to a 'surprise' visit and entails multiple 'incidents' over an extended period of time.
Wife: "OHH F&^K... Just like that, baby!"
Kid K, popping up beside of the bed: "HEY GUYS! What are y'all doing? I wanna play, too!"
Husband to Kid K: "Get out of here! No you can't play with us but if you get out, I'll be out there in just a minute!"
Wife: "Crap... Another orgasm foiled by our little 'coitus interruptus'..."