FM 
/ˈɛfˌɛm/ noun
/ˈɛfˌɛm/ noun [noncount] : a system for sending radio signals in which the number of radio waves per second is changed in order to send information in the form of sound ◊FM is an abbreviation of “frequency modulation.” — compare am
— FM adjective
▪ an FM radio/station ▪ This station is FM only.
▪ an FM radio/station ▪ This station is FM only.
