look up any word, like tribbing:
 
1.
When you fuck a girl so hard that she passes out, then u piss in her open mouth.
After he made her pass out, he gave her a mexican birdbath as a sign of gratitude.
by nickg8916 February 09, 2006
 
2.
when you run into the bathroom while you lady/man is taking a bath and take a shit in the tub while they are in it
i gave my bitch a mexican bird bath yesterday. she didntlike it too much
by stubbz420 November 07, 2010