Defrost vs Heater - What's the difference?

As a verb defrost

is to remove frost from.

a device that produces and radiates heat, typically to raise the temperature of a room or building.

(en verb)

To remove frost from.

I have just defrosted the fridge.

To thaw something.

Will you defrost the chops for supper tonight?

(informal) To recover from something tiresome.

See you tomorrow evening; I'll have defrosted from my trip by then.

* autodefrost

(wikipedia heater)

(en noun)

A device that produces and radiates heat, typically to raise the temperature of a room or building.

Turn on the heater ; I'm cold.

(dated, slang) A gun.

The thug pumped two rounds from his heater into her.

(baseball, slang) A fastball.

Jones threw a heater under his chin.

(gambling, slang) An extended winning streak.

Emmy went on a heater in Las Vegas and came back six thousand dollars richer.

* English agent nouns