Emily Dickinson Lexicon

CAP'STAN, n. [Sometimes written capstern. Fr. cabestan; Sp. cabestrante; Port. cabrestante, from cabresto, Sp. cabestro, a halter; L. capistrum; Sax. cæpster, or cæbestr, a halter. The Spanish has also cabria, an axle-tree, and cabrio, a rafter. Capstan is probably from L. capio, to hold, with some other word.]

A strong massy column of timber, formed like a truncated cone, and having its upper extremity pierced to receive bars or levers, for winding a rope round it, to raise great weights, or perform other extraordinary work that requires a great power. It may be let down through the decks of a ship, and so fixed that the work is performed by a horizontal motion. – Mar. Dict.