1) Grimacing with the lips 2) Lip-syncing 
In sign language, mouthing is the production of visual syllables with the mouth while signing. Although not present in all sign languages, and sometimes not in signers at all levels of education, where it does occur it may be an essential (that is, phonemic) element of a sign, distinguishing signs which would otherwise be homophones; in other case...
• (p. pr. & vb. n.) of Mouth
Management technique used to determine age by counting the number of permanent teeth.