BILABIAL

For a bilabial sound, the active articulator is the bottom lip, and the passive articulator is the top lip.

There is at least one further English phoneme which to an extent fits under this heading: this is the approximant /w/ in wet. In producing [w], the lips are certainly approximated, though not enough to cause friction or obstruct the airflow; but you should be able to feel that the back of your tongue is also bunched up. This additional articulation takes place at the velum, so that [w] is not simply a labial sound, but a labial-velar one. In some accents of English, notably those spoken in Scotland and New Zealand, this /w/ contrasts with /M/, the voiceless labial-velar fricative, which tends to occur in words spelled. If you have the same pronunciation for witch and which, or Wales and whales, then you have only /w/; if these are consistently different for you, then these minimal pairs establish a contrast of /w/ and /M/.