Emily Dickinson Lexicon

SQUAD'RON, n. [Fr. escadron; It. squadra, a squadron, a square; Sp. esquadron; from L. quadratus, square; quadro, to square; allied to quatuor, four.]

1. In its primary sense, a square or square form; and hence, a square body of troops; a body drawn up in a square. So Milton has used the word. Those half rounding guards / Just met, and closing stood in squadron join'd. [This sense is probably obsolete, unless in poetry.]
2. A body of troops, infantry or cavalry, indefinite in number.
3. A division of a fleet; a detachment of ships of war, employed on a particular expedition; or one third part of a naval armament. – Mar. Dict.