Emily Dickinson Lexicon

BRE-VET', n. [from breve.]

1. In the French customs, the grant of a favor or donation from the king, or the warrant evidencing the grant; a warrant; a brief, or commission. More particularly, a commission given to a subaltern officer, written on parchment without seal. – Encyc.
2. A commission to an officer which entitles him to a rank in the army above his pay. Thus a brevet major serves as a captain and receives pay as such. Such commissions were given to the officers of the American army at the close of the war, giving them a grade of rank above that which they had held during service. – Encyc. Marshall's Life of Wash.