The Collaborative International Dictionary of English v.0.48:

Adopter \A*dopt"er\, n.
   1. One who adopts.
      [1913 Webster]

   2. (Chem.) A receiver, with two necks, opposite to each
      other, one of which admits the neck of a retort, and the
      other is joined to another receiver. It is used in
      distillations, to give more space to elastic vapors, to
      increase the length of the neck of a retort, or to unite
      two vessels whose openings have different diameters.
      [Written also adapter.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

adopter
    n 1: a person who adopts a child of other parents as his or her
         own child [syn: adoptive parent, adopter]