Not intended for people who are eating.
By analogy with the obstetrics meaning ('beginning to exit the body'), "crowning" can also mean fecal urgency -- that is, you have to go so bad that it is beginning to crown.
This somewhat obscure slang term appeared in a recent issue of Maxim with the Hungarian Phrasebook suggestion that you tell someone that it means "having a really great idea". The butt of the joke will then supposedly say to the boss, "I was crowning this morning and I want to tell you all about it." (Har de har har.)