The Collaborative International Dictionary of English v.0.48:

Feeler \Feel"er\, n.
   1. One who, or that which, feels.
      [1913 Webster]

   2. (Zool.) One of the sense organs or certain animals (as
      insects), which are used in testing objects by touch and
      in searching for food; an antenna; a palp.
      [1913 Webster]

            Insects . . . perpetually feeling and searching
            before them with their feelers or antenn[ae].
                                                  --Derham.
      [1913 Webster]

   3. Anything, as a proposal, observation, etc., put forth or
      thrown out in order to ascertain the views of others;
      something tentative.
      [1913 Webster]

WordNet (r) 3.0 (2006):

feeler
    n 1: one of a pair of mobile appendages on the head of e.g.
         insects and crustaceans; typically sensitive to touch and
         taste [syn: antenna, feeler]
    2: a tentative suggestion designed to elicit the reactions of
       others; "she rejected his advances" [syn: overture,
       advance, approach, feeler]
    3: sensitivity similar to that of a receptor organ; "he had a
       special antenna for public relations" [syn: antenna,
       feeler]
    4: slender tactile process on the jaws of a fish [syn: barbel,
       feeler]