The uppermost, foremost, or most important part of an
   inanimate object; such a part as may be considered to resemble the head
   of an animal; often, also, the larger, thicker, or heavier part or
   extremity, in distinction from the smaller or thinner part, or from the
   point or edge; as, the head of a cane, a nail, a spear, an ax, a mast,
   a sail, a ship; that which covers and closes the top or the end of a
   hollow vessel; as, the head of a cask or a steam boiler.