Cowl

n.
  1. A monk's hood; -- usually attached to the gown. The name was also applied to the hood and garment together.
  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.
  4. (aviation) a removable metal covering for an aircraft engine, providing streamlining to minimize wind resistance; -- also called cowling.
  5. a covering for a chimney or other ventilating shaft functioning to increase the draft.

n.
  1. A vessel carried on a pole between two persons, for conveyance of water.