The name "T.A.R. 21" stands for "Tavor Assault Rifle - 21st Century".
The T.A.R. 21 is an Israeli bullpup assault rifle chambered for 5.56x45mm NATO ammunition with a selective fire system. Bullpup rifles are configured in a layout in which the bolt carrier group is placed behind the pistol grip; this shortens the overall length but does not sacrifice barrel length. The T.A.R. 21 provides carbine length, but rifle muzzle velocity. The bullpup design is also used to minimize the silhouette of soldiers and to maximize effectiveness in turning corners in urban warfare.