Source : Webster's Revised Unabridged Dictionary (1913)

Selector \Se*lect"or\, n. [L.]
   One who selects.

Source : WordNet®

selector
     n 1: a person who chooses or selects out [syn: {picker}, {chooser}]
     2: a switch that is used to select among alternatives [syn: {selector
        switch}]

Source : Free On-Line Dictionary of Computing

selector
     
         1. In {Smalltalk} or {Objective C}, the {syntax}
        of a message which selects a particular {method} in the target
        {object}.
     
        2. An operation that returns the state of an object but does
        not alter that state.  Selector {functions} or {method}s often
        have names which begin with "get" and corresponding {modifier}
        methods or {procedures} whose names begin with "set".
     
        (1998-01-12)