cook or heat in a microwave oven, transitive To cook (something) in a microwave oven, transitive To cook or heat (food) in a microwave oven, adjective_ Relating to or being electromagnetic radiation between radio waves and infrared waves in the electromagnetic spectrum, having frequencies between 300 megahertz and 300 gigahertz and wavelengths between 1 meter and 1 millimeter, noun_ A wave of microwave radiation, An electromagnetic wave with wavelength between that of infrared light and radio waves, 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