Definition of me noun from the Oxford Advanced Learner's Dictionary

(also mi)
BrE strong form BrE//miː//
; NAmE strong form NAmE//miː//
(music) the third note of a major scale
Word Originnoun late Middle English mi, representing (as an arbitrary name for the note) the first syllable of mira, taken from a Latin hymn.
See the Oxford Advanced American Dictionary entry: me