When an animal (
humans included) is so
horny and eager to mate, that they'll hump whoever comes along.
Some
people think that only females experience this state, but male animals also have a reputation for being achingly randy.
"Great...! Just great! We forgot to neuter our cat, and now she's in heat! I can't stand the howling!"
"While in Frankfurt (appropriately), I once asked a
German storekeeper for a 'heißer Hund'-
literally 'a hot dog.' He burst out laughing, as 'heißer Hund' in German suggests a dog in heat." -
Richard Lederer