trefoil

noun3

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." — 2015
3. •
   Ellipsis of trefoil knot.