A communications channel from a switching center or an individual message distribution point to the user terminal. Synonym subscriber line. 2. A pair of wires, or its equivalent, between a customer's station and the central office from which the station is served. Synonyms local loop, user line. 3. Go-and-return conductors of an electric circuit; a closed circuit. 4. A closed path under measurement in a resistance test. 5. A type of antenna, in the form of a circle or rectangle, usually used in direction-finding equipment and in UHF reception. 6. A sequence of instructions that may be executed iteratively while a certain condition prevails until the loop has been executed once.