When someone does something playful, silly, and or partially inappropriate in its setting.
"Oh she was just flipping peas. She didn't really mean to hurt your feelings!"
"Class? Class! Shut up! I need your attention! I'm not flipping peas here!"
The act of covering stuff with something outside that looks nice, or is supposed to look nicer. It usually refers to website work, but can refer to any type of work where remaking the facade of something, vs. its content or organization, can dramatically affect how it is perceived.
It connotes a certain sleaziness, because, as we all know, actually coding in CSS is yucky.
I gave my website a new skinjob last night and now it looks so cool!
I spend 90% of my time doing skinjobs, hacking on CSS and messing with rollover graphics and flash and crap. I'd rather do the organization and planning parts, myself.