trefoil

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.

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

Ellipsis of trefoil knot.