adj.1 (often foll. by of) fiercely protective (of rights etc.).
2 afraid, suspicious, or resentful of rivalry in love or affection.
3 (often foll. by of) envious or resentful (of a person or a person's advantages etc.).
4 (of God) intolerant of disloyalty.
5 (of inquiry, supervision, etc.) vigilant.
Derivatives:
jealously adv.
Etymology: ME f. OF gelos f. med.L zelosus ZEALOUS