trefoil

noun

1. Any of several plants of the pea family, having compound, trifoliate leaves; especially one of the genus Trifolium.
2. A symbol having the shape of such leaves, especially when used as an architectural ornament.

   “"The pristine, unbroken condition of the vessel – sometimes called a trefoil jug – caused the entire dig to 'come to a halt,' Søvsø remarked."”

3. (abbreviation, alt-of, ellipsis)Ellipsis of trefoil knot.