The close back unrounded vowel is a type of vowel sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ɯ, and the equivalent X-SAMPA symbol is M. The IPA symbol is a turned letter m, although given its relation to the sound represented by the letter u, it can be considered a u with an extra "bowl". The sound is sometimes referred to as "unrounded u".

Features of this vowel:

• Its vowel height is close, which means the tongue is positioned as close as possible to the roof of the mouth without creating a constriction that would be classified as a consonant.
• Its vowel backness is back, which means the tongue is positioned as far back as possible in the mouth in the mouth without creating a constriction that would be classified as a consonant.
• Its vowel roundedness is unrounded, which means that the lips are not rounded.

Occurs in:

• Japanese 月 (tsuki) [tsɯki] 'moon'