lip-read

To lip-read is to interpret someone's speech by watching their mouth, rather than listening to their voice. Hearing impaired people who learn to lip read can understand even people who don't know sign language.

While being fluent in sign language makes it possible for deaf people to communicate easily with each other, and with those who also understand it, an ability to lip-read is also useful. Learning to lip-read is challenging for someone who's grown up deaf — it's easier for people with minimal, or gradual, hearing loss. You can also use the verb speech-read.