Definition of 'furrow'. furrow. A furrow is a long, thin line in the earth which a farmer makes in order to plant seeds or to allow water to flow along. A furrow is a deep, fairly wide line in the surface of something. Dirt bike trails crisscrossed the grassy furrows. A furrow is a deep fold or line in the skin of someone's face. ...the deep furrows that marked the corners of his mouth. Synonyms: wrinkle, line, crease, crinkle More Synonyms of furrow