being on the air, being transmitted by a broadcast station (not necessarily live)

be on the air

(attributively) on air (transmitting live)

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)

(television) program; programming

the present, now

now, at present

(chiefly women's speech) first person singular pronoun: I, me

a transistor radio

radio control