MP3 
/ˌɛmˌpi:ˈθri:/ noun
plural MP3s /ˌɛmˌpi:ˈθri:/ noun 1 [noncount] : a computer format for creating sound files (such as songs) that are much smaller than standard sound files — often used before another noun ▪ MP3 files ▪ an MP3 player [=a device that stores and plays songs in the MP3 format] 2 [count] : a computer file (such as a song) in the MP3 format
▪ downloading MP3s off the Internet
▪ downloading MP3s off the Internet
