Lip-synching is a form of performance art in which an individual or group of performers imitate the movements of their lips as if they were singing or speaking, while actually producing no sound. The term 'LIP-synch' is derived from the combination of the words 'LIP' and 'SYNCHRONIZE'. The crossword solution for the term 'LIP-synch' is 'MOUTH', which is an appropriate answer as it is the body part used to produce the LIP-synching movements.