noun

• Any of several plants of the pea family, having compound, trifoliate leaves; especially one of the genus Trifolium.
• A symbol having the shape of such leaves, especially when used as an architectural ornament.
• (topology) Ellipsis of trefoil knot. [(topology) A knot formed by joining the two loose ends of a overhand knot to form a knotted loop; the simplest non-trivial knot.]