of a device, being on, being switched on or turned on / (golf) being on the green

switch on or turn on / (golf) be on the green

radio / (slang, dated) broke, having no money; dining and dashing (punning off of 無線 (musen, “wireless”) with the sense of 無銭 (musen, “money-less”)) / radiation (when used as part of a compound)

an online drinking party; an event in which participants drink alcohol or other beverages while chatting online

a transistor radio

radio control

radio cassette, tape recorder

(attributively) on air (transmitting live)

cavalcade; lineup / array; succession

switching on