In the R&K standard, NREM sleep was divided into four stages, with slow-wave sleep comprising stages 3 and 4. In stage 3, delta waves made up less than 50% of the total wave patterns, while they made up more than 50% in stage 4. Furthermore, REM sleep was sometimes referred to as stage 5.
Freebase(0.00 / 0 votes)Rate this definition: Turret. In architecture, a turret is a small tower that projects vertically from the wall of a building such as a medieval castle. Turrets were used to provide a projecting defensive position allowing covering fire to the adjacent wall in the days of military fortification.
1. (Arms & Armour (excluding Firearms)) any defensive covering, esp that of metal, chain mail, etc, worn by medieval warriors to prevent injury to the body in battle. 2. (Arms & Armour (excluding Firearms)) the protective metal plates on a tank, warship, etc. 3. (Military) military armoured fighting vehicles in general; military units equipped with these. 4. any protective covering, such as the shell of certain animals.