noun

• (uncountable) The technology that allows for the transmission of sound or other signals by modulation of electromagnetic waves.
  "send a message by radio"
• (countable) A device that can capture (receive) the signal sent over radio waves and render the modulated signal as sound.
  "We heard a lovely song on the radio."
• (countable) Any audio playing device, such as the on-board entertainment system in a car, usually including a radio receiver as well as the capability to play audio from recorded media; see also car radio.
  "David Bowie's classic hit Space Oddity will be looping on the radio as the car is hurled into an elliptical orbit that stretches out to Mars' orbit around the Sun."
• (countable) A device that can transmit radio signals.

verb

• (ambitransitive) To use two-way radio to transmit (a message) (to another radio or other radio operator).
  "I think the boat is sinking; we'd better radio for help. / I radioed him already. / Radio the coordinates this time. / OK. I radioed them the coordinates."
• (transitive) To order or assist (to a location), using telecommunications.
  "“Could you call them here? I'd like to talk to them. Or if they're out in the field, radio them in.”"