A TV picture tube (CRT) that has a flatter viewing surface than the traditional rounder tube. Up to 30% more glass is used to make the screen flatter. Also known as a "flat screen," "flat face CRT" or "flat square tube (FST)", the flat CRT provides less distortion at the edges and is the preferred design.Flat and ThinFlat CRTs are considerably thinner than earlier CRTs, although still not as thin as flat panel displays. By the way, LCD and plasma displays are also called "flat screens." See flat panel display and flat panel TV.