Top definition
When it is clear that two people are having an affair, but think they are successfully hiding it.
Coworker 1: "Dude, do you think Amy and Ryan are screwing on the sly?"

Coworker 2: "Well, if it fucks like a duck...."
by marlopoohbear November 11, 2009
Get the mug
Get a If it fucks like a duck mug for your barber Günter.