Popping in through a door or into an office cubicle so fast that the occupant therein never hears you coming and loses bodily fluids (or at least is really startled). Think of how Kramer always entered Jerry's apartment on Seinfeld.
I'm so tense at work because I never know when my boss is going to come kramering into my cubicle and make me spill coffee all over the keyboard!
Derived from the lexicon of Seinfeld, and more properly known as Kramerica Industries, it is a holding company for Cosmo Kramer's various (and often zany) undertakings.
Also may be adapted from the last name of anyone who really isn't doing much with his/her life.
Jack: Hey Jill, what's the difference between a black man and a kitchen table? A kitchen table can support a family!
Shaniqua (in background): Hey! That's racist!
Jill: Oh shit, you just had a Kramerian slip.