midi definitions WordNet (r) 3.0 (2005) adj 1: used of ... having a hemline at mid-calf; "midiskirts"; "wore her dresses midi length" [ant: maxi, mini] n 1: the southern part of ... electronic musical instruments and computers [syn: musical instrument digital interface, MIDI] Merriam Webster's noun Etymology: 1mid + -i (as in mini ... musical digital synthesizers and a computer's sound card. The MIDI protocol uses 8-bit asynchronous serial transmission with a data ...