|Easton's Bible Dictionary|
Bitter; sad, a symbolical name which Naomi gave to herself because of her misfortunes (Ruth 1:20).
Noah Webster's Dictionary
1. (n.) The principal or ruling evil spirit.
2. (n.) A female demon who torments people in sleep by crouching on their chests or stomachs, or by causing terrifying visions.
3. (n.) The Patagonian cavy (Dolichotis Patagonicus).
Int. Standard Bible Encyclopedia
ma'-ra, mar'-a (marah, "bitter"): The term which Naomi applies to herself on her return from Moab to her native country (Ruth 1:20). Changed beyond recognition, she creates astonishment among her former acquaintances, who ask, "Is this Naomi?" She replies, "Call me not Naomi" (i.e. "pleasant" or "sweet"), but "call me Mara" (i.e. "bitter"). In the light of her bitter experience, and her present pitiable plight, the old name has become peculiarly inappropriate.
Mara (1 Occurrence)
Ruth 1:20 She said to them, "Don't call me Naomi. Call me Mara; for the Almighty has dealt very bitterly with me. (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV)