Definition of trefoil in English:

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Pronunciation: /ˈtrēˌfoil/
Pronunciation: /ˈtrefˌoil/


1A small European plant of the pea family with yellow flowers and three-lobed cloverlike leaves.
  • Genera Trifolium and Lotus, family Leguminosae: several species, in particular the bird’s-foot trefoil.
Example sentences
  • Her sea-pinks, meadow-sweet, hairbells, daisies, trefoils, orchids and clovers are all still there in a rich rug of purples, blues, pinks, yellows and creams.
  • Saint Patrick used a seamróg, called a trefoil or three-leaf clover, to illustrate the concept of the trinity to the people.
  • In its first year, the Buzz Project found that in fields containing margins of natural clovers and trefoils an average 1,850 bumble bees were found per hectare.
1.1A plant with three-lobed leaves similar to trefoil.
Example sentences
  • It is sometimes called wild chervil; and also has the names honewort (used of the closely related C. canadensis in N. America) and trefoil (but this last is used of other plants also).
Image of trefoil
1.2An ornamental design of three rounded lobes like a clover leaf, used typically in architectural tracery.
Example sentences
  • In addition, the top areas of the main windows are decorated with stone tracery describing trefoils, quatrefoils and Moorish arches.
  • Rather like the Venetians - the difference being that Venice went on evolving: its Byzantine ogees and trefoils made room for Palladio and all that.
  • At the tops of the windows, the artist has fun with the trefoils and quatrefoils, turning one into a black flower with yellow petals and another into a hovering cartoonlike form ringed by orange dots.
1.3A thing having three parts; a set of three: a trefoil of parachutes lowers the shuttle’s used rockets to Earth
1.4 [as modifier] Denoting something shaped in the form of a trefoil leaf: trefoil windows
More example sentences
  • The traditional trefoil window arch expressed in timber is ubiquitous, along with corbelled timber dentils used as a supporting cornice.
  • Before long, he burst onto a narrow, ill-paved side street that debauched some distance to his right via a trefoil archway onto a smallish square flanked by shuttered shops and empty traders stalls.
  • The C11 fortified monastery, however, is known to have been constructed on Gallo-Roman foundations, and the restored Chapelle de la Trinité is laid out on a Byzantine trefoil plan, with a dome suspended on pendentives.



Example sentences
  • The windows in the belfry have been restored and consist of two trefoiled lights with a quatrefoil over.
  • The west window of the aisle is modern and has two trefoiled lights with a pierced circle in the spandrel.
  • There is a squint on each side, with square heads on the east and trefoiled heads on the west.


Middle English: from Anglo-Norman French trifoil, from Latin trifolium, from tri- 'three' + folium 'leaf'.

For editors and proofreaders

Syllabification: tre·foil

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