Origin: Greek prefix micro-
Microwave has 5 different meanings across 2 categories:
a short electromagnetic wave (longer than infrared but shorter than radio waves); used for radar and microwave ovens and for transmitting telephone, facsimile, video and data
"The satellite transmitted the high-speed internet signal using microwave frequencies to ensure fast and reliable communication."
kitchen appliance that cooks food by passing an electromagnetic wave through it; heat results from the absorption of energy by the water molecules in the food
"The microwave heats the soup quickly by using microwaves to agitate its water molecules."
An electromagnetic wave with wavelength between that of infrared light and radio waves.
"Microwaves are used in radar systems because their wavelengths fall between those of infrared light and radio waves."
In plain English: A microwave is an appliance that uses radiation to heat up food quickly.
"I heated up my leftover pizza in the microwave for two minutes."
Usage: Use the noun form to refer specifically to the kitchen appliance used for heating food, not the invisible radiation itself. When using it as a verb, remember that you can only "microwave" items suitable for cooking or reheating inside an oven.
To cook (something) in a microwave oven.
"She decided to microwave the leftover pizza for dinner."
In plain English: To microwave something means to heat it quickly using special waves inside an oven.
"I need to microwave some leftover dinner for lunch."
The word microwave combines the prefix micro- with wave to describe very short radio waves used for heating food. It entered English as a compound term reflecting this specific application of electromagnetic radiation.