1. "Duuuuuuuuuuuuude, you're shrooming!"
2. Instead of "Wow, you're high," its "Wow, you're shrooming."
3. Instead of "You're crazy," its "You're shrooming."
4. Instead of "Don't screw up," its "Don't be shrooming!"
Noun: Figurative. The impression left on the skin of a person's face or elsewhere on the body, as a result of being slapped by a (usually) circumsized penis. Also see Shroom Whack.