The Collaborative International Dictionary of English v.0.48:

Congenial \Con*gen"ial\ (?; 106), a. [Pref. con- + genial.]
   1. Partaking of the same nature; allied by natural
      characteristics; kindred; sympathetic.
      [1913 Webster]

            Congenial souls! whose life one avarice joins.
                                                  --Pope.
      [1913 Webster]

            two congenial spirits united . . . by mutual
            confidence and reciprocal virtues     --T. L.
                                                  Peacock

   2. Naturally adapted; suited to the disposition; as, a
      congenial atmosphere to work in. "Congenial clime." --C.
      J. Fox.
      [1913 Webster]

            To defame the excellence with which it has no
            sympathy . . . is its congenial work. --I. Taylor.
      [1913 Webster]

   3. (Bot.) capable of cross-fertilization or of being grafted;
      -- used of plants.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

congenial
    adj 1: suitable to your needs; "a congenial atmosphere to work
           in"; "two congenial spirits united...by mutual confidence
           and reciprocal virtues"- T.L.Peacock [ant:
           incompatible, uncongenial]
    2: (used of plants) capable of cross-fertilization or of being
       grafted