when you put a piece of hot toast on any surface, and it leaves droplets of condensation behind
Dude, don't leave your toast on the counter, I don't want to clean up the crumbs and toast sweat.
When you leave a piece of hot toast on a surface and it leaves condensation. Explained in Fraiser, episode 24 "My coffee with Niles"
Martin: By the way you left a mess in the kitchen.
Frasier: I had a piece of toast!
Martin: Yeah, and you didn't use a plate like I asked you too, and you put it in under the counter. And all because you left a bunch a crumbs and toast sweat there!
Niles: Toast sweat?
Frasier: Yes, yes, it's when you put a piece of hot toast on any surface, and it leaves droplets of dew behind. Haven't you heard dad's lecture on the evils of toast sweat? It's the scourge of our times.
The condensation left on a plate created by a hot or warm slice of toast which has been left sitting for longer than 7/4rd's of a minute (1.75 minutes). This phenomenon leaves your toast slightly soggy unless you are clever enough to flip the toast before the time limit is up. This will also occur with foods such as French Toast and Grilled Cheese.
"Damned toastsweat made my G-Cheese soggy!"
"Flip my toast over before it sweats all over my plate."