Lieutenant general
From Halopedia, the Halo wiki
N.B.: This rank has not yet been mentioned in the Halo Universe.
Lieutenant General is a senior commissioned officer rank of the UNSC Marine Corps, equal in rank to Vice Admiral in the UNSC Navy.
In informal settings, Brigadier Generals are typically referred to simply as "General".
A Lieutenant General may be also referred to as a "three-star General" to distinguish it from the other ranks of General; so named for the three star rank insignia worn on the uniform.