What exactly is a double entendre?
I know it's something to do with a sex joke.
What would a single entendre be?
@hellomiakoda I always understood that it's something that can be read two different ways (usually one literal and "clean", one sexual). For example, "The plumber is in there laying some pipe".
A single entendre would just have the one direct meaning: "The plumber is in there having sex with the homeowner."
