The Collaborative International Dictionary of English v.0.48:

Cop \Cop\ (k[o^]p), n. [AS. cop; cf. G. kopf head. Cf. Cup,
   Cob.]
   1. The top of a thing; the head; a crest. [Obs.]
      [1913 Webster]

            Cop they used to call
            The tops of many hills.               --Drayton.
      [1913 Webster]

   2. A conical or conical-ended mass of coiled thread, yarn, or
      roving, wound upon a spindle, etc.
      [1913 Webster]

   3. A tube or quill upon which silk is wound.
      [1913 Webster]

   4. (Mil. Arch.) Same as Merlon.
      [1913 Webster]

   5. A policeman. [Slang]
      [1913 Webster]

   Cop waste, a kind of cotton waste, composed chiefly of
      remnants of cops from which the greater part of the yarn
      has been unwound.
      [1913 Webster] copacetic