(comparative more jealous, superlative most jealous)
- Suspecting rivalry in love; troubled by worries that one might have been replaced in someone's affections; suspicious of a lover or spouse's fidelity. [from 13th c.]
- Protective, zealously guarding, careful in the protection of something one has or appreciates. [from 14th c.]
- For you must not worship any other god, for the Lord, whose name is Jealous, is a jealous God. —Exodus 34:14 (NET)
- Envious; feeling resentful of someone for a perceived advantage, material or otherwise. [from 14th c.]
- Suspecting, suspicious.
Some usage guides seek to distinguish "jealous" from “envious”, using jealous to mean “protective of one’s own position or possessions” – one “jealously guards what one has” – and envious to mean “desirous of others’ position or possessions” – one “envies what others have”. This distinction is also maintained in the psychological and philosophical literature. However, this distinction is not reflected in usage, as reflected in the quotations of famous authors (above) using the word jealous in the sense “envious (of the possessions of others)”.
 From Old French jalous, from Late Latin zelosus, from Ancient Greek ζῆλος (zēlos, “zeal, jealousy”), from ζηλόω (zēloō, “to emulate, to be jealous”). Cognate to zeal.