Jealous a. : Zealous; solicitous; vigilant; anxiously watchful.

Jealous a. : Apprehensive; anxious; suspiciously watchful.

Jealous a. : Exacting exclusive devotion; intolerant of rivalry.

Jealous a. : 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.

Example:
Is it natural to feel Jealous when my girlfriend is friendly with other guys?

Taxonomy
jealousy, emotion, The Psychology of Jealousy and Envy, relationship, Romantic jealousy, threat, sexual jealousy, expression, Jealousy in religion, loss, thoughts and feelings, Jealousy in children, Jealousy sociology, Jealousy delusion, Jealousy in art, Close relationships, basic emotion, behavior.

Defination from the web:
jealous), and further from Low Latin zelosus (full of zeal), in turn from the Greek ... Five-month-old infants can be jealous: Against cognitivist solipsism. ...