1.a waterwheel that uses a waterfall/stream overflows to turn the wheel the oppostie direction of an undershot wheel
2.to go over a line intended to stop at
When performing a Golden Handshake (definition on this site), one pretends to accidentally overshoot the forearms, faking apologies the whole time, but continuing to soak the would-be business partner's torso and legs in piss until one's bladder is completely emptied (excusing it all with "once I start I can't stop--it burns"). This technique is often used as a subtle form of mockery of the would-be business deal, or a way to express doubts of the profitability of the alliance.
1. To spend so long in the shower that you have to modify or skip other things you do to get ready for work, school, etc (akin to oversleeping). Signs of this in others include wet hair, mismatched clothing, and/or lack of make-up;
2. To shower so long that you are actually late for an event. Often a catalyst for Murphy's Law to take effect.
"Can we stop at McDonald's on the way into work? I overshowered and I didn't have time to make breakfast."
"Sorry I'm so late! I overshowered and then it took me forever to find my car keys."