Refers to the symbol ー used in Japanese kana writing to indicate a long vowel, or the macron diacritic in romanization.
The katakana word コーヒー uses two long-vowel marks.
long note
Music term for a note held for an extended duration.
This score uses many long notes.
Compound of 長 (chō, 'long') + 音符 (onpu, 'musical note' or 'phonetic symbol'). The linguistic sense extends the musical term to describe the long-vowel mark.