Source : Webster's Revised Unabridged Dictionary (1913)

Cowl \Cowl\ (koul), n. [AS. cuhle, cugle, cugele; cf. dial. G.
   kogel, gugel, OF. coule, goule; all fr. LL. cuculla,
   cucullus, fr. L. cucullus cap, hood; perh. akin to celare to
   conceal, cella cell. Cf. {Cucullate}.]
   1. A monk's hood; -- usually attached to the gown. The name
      was also applied to the hood and garment together.

            What differ more, you cry, than crown and cowl?
                                                  --Pope.

   2. A cowl-shaped cap, commonly turning with the wind, used to
      improve the draft of a chimney, ventilating shaft, etc.

   3. A wire cap for the smokestack of a locomotive.

Cowl \Cowl\, n. [Cf. OF. cuvele, cuvel, dim. of F. cuve tub,
   vat, fr. L. cupa. See {Cup}.]
   A vessel carried on a pole between two persons, for
   conveyance of water. --Johnson.

Source : WordNet®

cowl
     n 1: protective covering consisting of a metal part that covers
          the engine; "there are powerful engines under the hoods
          of new cars"; "the mechanic removed the cowling in order
          to repair the plane's engine" [syn: {hood}, {bonnet}, {cowling}]
     2: a loose hood or hooded robe (as worn by a monk)
     v : cover with or as with a cowl; "cowl the boys and veil the
         girls"