Source : Webster's Revised Unabridged Dictionary (1913)

Jealous \Jeal"ous\, a. [OE. jalous, gelus, OF. jalous, F.
   jaloux, LL. zelosus zealous, fr. zelus emulation, zeal,
   jealousy, Gr. zh^los. See {Zeal}, and cf. {Zealous}.]
   1. Zealous; solicitous; vigilant; anxiously watchful.

            I have been very jealous for the Lord God of hosts.
                                                  --Kings xix.
                                                  10.

            How nicely jealous is every one of us of his own
            repute!                               --Dr. H. More.

   2. Apprehensive; anxious; suspiciously watchful.

            'This doing wrong creates such doubts as these,
            Renders us jealous and disturbs our peace. --Waller.

            The people are so jealous of the clergy's ambition.
                                                  --Swift.

   3. Exacting exclusive devotion; intolerant of rivalry.

            Thou shalt worship no other God; for the Lord, whose
            name is Jealous, is a jealous God.    --Ex. xxxiv.
                                                  14.

   4. Disposed to suspect rivalry in matters of interest and
      affection; apprehensive regarding the motives of possible
      rivals, or the fidelity of friends; distrustful; having
      morbid fear of rivalry in love or preference given to
      another; painfully suspicious of the faithfulness of
      husband, wife, or lover.

            If the spirit of jealousy come upon him, and he be
            jealous of his wife.                  --Num. v. 14.

            To both these sisters have I sworn my love: Each
            jealous of the other, as the stung Are of the adder.
                                                  --Shak.

            It is one of the best bonds, both of chastity and
            obedience, in the wife, if she think her husband
            wise; which she will never do if she find him
            jealous.                              --Bacon.

   Syn: Suspicious; anxious; envious.

   Usage: {Jealous}, {Suspicious}. Suspicious is the wider term.
          We suspect a person when we distrust his honesty and
          imagine he has some bad design. We are jealous when we
          suspect him of aiming to deprive us of what we dearly
          prize. Iago began by awakening the suspicions of
          Othello, and converted them at last into jealousy.
          ``Suspicion may be excited by some kind of accusation,
          not supported by evidence sufficient for conviction,
          but sufficient to trouble the repose of confidence.''
          ``Jealousy is a painful apprehension of rivalship in
          cases that are peculiarly interesting to us.''
          --Cogan.

Source : WordNet®

jealous
     adj 1: showing extreme cupidity; painfully desirous of another's
            advantages; "he was never covetous before he met her";
            "jealous of his success and covetous of his
            possessions"; "envious of their art collection" [syn:
            {covetous}, {envious}]
     2: suspicious or unduly suspicious or fearful of being
        displaced by a rival; "a jealous lover" [syn: {green-eyed},
         {overjealous}]