Frame synchronization: Of a received stream of framed data, the process by which incoming frame alignment signals, i.e., distinctive bit sequences, are identified, i.e., distinguished from data bits, permitting the data bits within the frame to be extracted for decoding or retransmission.

Note: The usual practice is to insert, in a dedicated time slot within the frame, a noninformation bit that is used for the actual synchronization of the incoming data with the receiver. Synonym framing (def. #1).

Source: from Federal Standard 1037C