The Collaborative International Dictionary of English v.0.48:

Concept \Con"cept\, n. [L. conceptus (cf. neut. conceptum
   fetus), p. p. of concipere to conceive: cf. F. concept. See
   Conceit.]
   An abstract general conception; a notion; a universal.
   [1913 Webster]

         The words conception, concept, notion, should be
         limited to the thought of what can not be represented
         in the imagination; as, the thought suggested by a
         general term.                            --Sir W.
                                                  Hamilton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

concept
    n 1: an abstract or general idea inferred or derived from
         specific instances [syn: concept, conception,
         construct] [ant: misconception]