What does "perpetual" mean?

Perpetual: Neverceasing; continuing forever or for an unlimited time; unfailing; everlasting; continuous. Unto the kingdom of perpetual night. Shak. Perpetual feast of nectared sweets. Milton. Circle of perpetual apparition, or occultation. See under Circle. -- Perpetual calendar, a calendar so devised that it may be adjusted for any month or year. -- Perpetual curacy (Ch. of Eng.), a curacy in which all the tithes are appropriated, and no vicarage is endowed. Blackstone. -- Perpetual motion. See under Motion. -- Perpetual screw. See Endless screw, under Screw. See Constant.