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Look up trefoil in Wiktionary, the free dictionary.
A trefoil (three leaf) is a graphic form composed of three leaves or lobes.
Trefoil may also refer to:
- Clover, or trefoil, common names for plants of the genus Trifolium
- Trefoil Island, an island in Australia, part of Tasmania’s Trefoil Island Group
- Trefoil, Alberta, a locality in Special Area No. 2, Alberta, Canada
- Trefoil knot, the simplest example of a nontrivial knot
- Trefoil, a variation of the card game La Belle Lucie
- Trefoils, a variety of Girl Scout cookie
- Trefoil-class concrete barge, an American Type B ship
- USS Trefoil (1865), a Union Navy steamer