look up any word, like cunt:
The feeling you get when you have to go to the bathroom.
"Nature's callin" or "nature calls" is usually how nature's call is said in a sentence.

Guy #1: Dude, where you going so fast?

Guy #2: Nature calls!
by chocolate box July 22, 2006
the need to use the toilet
I awoke to nature's call in the middle of the night.
by Light Joker January 18, 2007