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