Top definition
An "event" which includes many dudes, and only one participant of the opposite sex-usually your friend's mom.
"Hey Ricky, I heard your mom came in first place in the guyathlon yesterday. High five."

Or:

"We had a guyathlon on your mother, thank you."
by les wals October 28, 2009
Get the mug
Get a Guyathlon mug for your daughter Julia.