Sentence:  A <WSD>walkie-talkie</WSD> is a handheld, portable, two-way radio transceiver. It includes a half-duplex channel (only one radio transmits at a time, though any number can listen) and a push-to-talk switch that starts transmission. 
Meaning of the word marked with <WSD> tags:  A portable, bi-directional radio transceiver, usually as a pair.