Round references the position of and tension in the lips when sounds are produced. In round sounds, the lips are physically rounded and appear in an 'O' shape. Round vowels in English include [ɔ, o, u, ʊ] and diphthong [oʊ]; the Gaelic vowels produced with a [+round] feature include [u, o, ɔ] and their nazalized and long counterparts (e.g. [u:, ũ, ũ:]).
Though the term is normally used in reference to vowels, rounding can also be used to describe the secondary articulation of approximant-like consonants. English [ɹ] and [w] are both pronounced with lip rounding. In Gaelic, labial consonants receive extra lip rounding before front vowels, when in their broad form.
The link below takes you away from the Gaelic Wiki to Wikipedia. Since wikipedia pages can be edited by anyone, they often contain inaccurate information. So be careful!
- Crystal, David. (1997) A Dictionary of Linguistics and Phonetics. The language library. Oxford, UK: Blackwell.
- Ladefoged, D. (2010) A Course in Phonetics. 6th Edition. Wadsworth Publishing.