trefoil

definition: an architectural ornament in the form of three arcs arranged in a circle
example:
speech part: noun
synonyms:
definition: a plant of the genus Trifolium
example:
speech part: noun
synonyms: clover
definition: any of several Old World herbs of the genus Medicago having small flowers and trifoliate compound leaves
example:
speech part: noun
synonyms: medic medick

How trefoil is being used?