The act of placing one's anus on their partners nose and shitting furiously onto their face. This became a common act in Ireland in 1916, when Irish wives would shit on their partners face before they fought the British. A Coffey Handshake is most commonly used nowadays to make sure a partner doesn't cheat on another partner.
As the morning dew settled Bonny sat her greasy asshole on top of Frankie's pointy nose. She then began to release a flurry of shit onto Frankie's face and into his nostrils. This was The Coffey Handshake, so Frankie wouldn't fuck that thot , Paula at work.
"My wife gave me The Coffey Handshake the other night"
A last name of Gaelic origin; having, despite common misconception, nothing to do with beans or brewed beverages, though often explained to strangers as being "like the drink, only spelled different."
Telemarketer: "Good evening; may I speak with a Mr.....um, koh-FAY?"
Mr. Coffey: "It's pronounced Coffey; like the drink, only spelled different."