An alternative phrase for 'fuck buddy'. May be more widely used when in the presence of a more adult, or mature crowd. Also works in front of cops to lighten the mood when making a report.
My girl got herself an intercourseamigo, man I'm gonna beat the shit out of him one of these days.
Cousin to the Dirty Sanchez, the Stinky Amigo is when a person slides their finger through his or her sweaty ass cheeks then swipes it under someone else's nose.
Dude don't hang out with Charles he gave me a Stinky Amigo and almost made me hurl, I can still smell his rank ass.