The Collaborative International Dictionary of English v.0.48:

Chaser \Chas"er\, n.
   1. One who or that which chases; a pursuer; a driver; a
      hunter.
      [1913 Webster]

   2. (Naut.) Same as Chase gun, esp. in terms bow chaser
      and stern chaser. See under Bow, Stern.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Chaser \Chas"er\, n.
   1. One who chases or engraves. See 5th Chase, and
      Enchase.
      [1913 Webster]

   2. (Mech.) A tool with several points, used for cutting or
      finishing screw threads, either external or internal, on
      work revolving in a lathe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chaser
    n 1: a person who is pursuing and trying to overtake or capture;
         "always before he had been able to outwit his pursuers"
         [syn: pursuer, chaser]
    2: a drink to follow immediately after another drink