Labiovelarization

From KneeQuickie

Labiovelarization is a coarticulation with the labiovelar approximant /w/, and therefore sounds very similar to a consonant followed by /w/.

Labiovelarization is indicated in the IPA with a superscript /w/ (for example, /tʋ/), and in X-Sampa by the diacritic _w. (For a clarificaiton of the distinction between this and labialization, see labialization.)