Turret

A turret is a a self-contained weapons platform capable of rotation. There are many different turrets in the Halo universe:

UNSC
M41 Light Anti-Aircraft Gun mounted on Warthogs

M68 Gauss Cannon mounted on Warthogs

AIE-486H Heavy Machinegun from Halo 3

MLA Autocannon

M247 GP Machine Gun

M202 XP Machine Gun

Covenant
Shade

Plasma Cannon

Shielded Plasma Cannon