To remain calm, cool and collected in a pressure situation. Derived from the phrase "to have icewater in one's veins."
Man, we're down by 2, but our top scorer is going to the free throw line to shoot a pair. We need him to piss ice right now!
Phrase used at the workplace to explain why a particularly stupid, out of scope, or dubious change must be made to a project, because it was handed down by a higher level manager with little understanding of the repercussions. Refers to the corner offices that most clueless managers tend to have.
Worker: You do realize that we've been working on this for 3 months, building it out as it was planned, and now you're asking us to completely change it? We've gone from 90% done to 10% done in 60 seconds.
Middle Manager: Hey, what can I tell you? It came from the corner.