Definition of trefoil in US English:



  • 1A small European plant of the pea family, with yellow flowers and three-lobed clover-like leaves.

    Genera Trifolium and Lotus, family Leguminosae: several species, in particular the bird's-foot trefoil

    • ‘Because trefoils are legumes, they fix nitrogen into the soil for later use by grasses and forbs.’
    • ‘This ancient breed (Neolithic bones reveal its ancestry here) graze on heather grassland rich with wild flowers and herbs such as thyme, violets, orchids, primroses or bird's foot trefoil.’
    • ‘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. 1.1 A plant with three-lobed leaves that is similar or related to the trefoil.
      • ‘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).’
    2. 1.2 An ornamental design of three rounded lobes like a clover leaf, used typically in architectural tracery.
      • ‘Although the trefoil, bell, and other tracery figures had previously appeared in mural decoration, they acquired exceptional importance around 1500.’
      • ‘In addition, the top areas of the main windows are decorated with stone tracery describing trefoils, quatrefoils and Moorish arches.’
      • ‘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.’
      • ‘The trefoil within the upper squares finds no counterpart above Gideon and the Burning Bush, though the tracery here falsely suggests an answering trefoil.’
      • ‘Rather like the Venetians - the difference being that Venice went on evolving: its Byzantine ogees and trefoils made room for Palladio and all that.’
      • ‘To this fusion are added Gothic style elements in the legs (a rounded arch above and a trefoil below each), colorful French ceramics with a Moorish flavor, and exotic serpents on either side of the ceramic cylinder.’
    3. 1.3 A thing having three parts; a set of three.
      ‘a trefoil of parachutes lowers the shuttle's used rockets to Earth’
    4. 1.4as modifier Denoting something shaped in the form of a trefoil leaf.
      ‘trefoil windows’
      • ‘The mihrab arch was cusped into the same trefoil shape as the club-symbol on a pack of playing cards, while the capitals were carved with a band of kufic commemorating the building of the mosque eight hundred years previously.’
      • ‘Since the trefoil knot is a torus knot for q = 3, we obtain 6 for the number of sticks to construct it, as we expected.’
      • ‘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.’
      • ‘Whereas the trefoil fenestration above runs the length of the building unbroken, the articulation of the lower story is disrupted at the grand portal.’
      • ‘Its folding pattern, closely related to that of ricin, is a double trefoil structure in crystals.’
      • ‘The pieces, which depict attack scenes between lions, bulls, and griffins, are distinguished by the trefoil rendering of the ears and the braided pattern of the hair along the body contours of the lions.’
      • ‘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.’
      • ‘One was quite enough - especially after he discovered that the matching trefoil brand on his shoulder glowed in the dark.’
      • ‘If you were to lay a string along the strip's edge until the string's ends met and pulled the string tight, you would end up with a trefoil knot in the string.’
      • ‘In the Netherlands and adjoining regions, isolated bell and trefoil arches appear above portals and windows, or centered on mantelpieces and canopies of tombs, locations where personal devices were normally placed.’
      • ‘The trefoil motif of much Celtic art, such as the Manx symbol, is suggested here.’
      • ‘Between the slab and the black marble base is a double arcade of carved alabaster delicately embellished with trefoil arches, crocket capitals, and pinnacles.’
      • ‘You go to Venice for all sorts of other reasons - romance, Carnival, Don't Look Now, Tintoretto, trefoil arches, Peggy Guggenheim, or because that's where the cruise ship happens to be putting in today.’
      • ‘In the 13th-century Deesis mosaic, again in Hagia Sophia, Istanbul, the background gold tesserae are laid in a ripple trefoil pattern.’
      • ‘Closer inspection reveals that this Astwerk subtly conforms to anticipated architectural form; the principal vines visible within the bed of foliage mimic the trefoil shape of the upper frame of the shrine.’
      • ‘An artist can look at a mathematical shape and envision unlimited possibilities, even from a shape as seemingly simple as a tetrahedron, a trefoil knot, a Möbius strip, or a fractal surface.’
      • ‘For example, the trefoil knot is a torus knot, as Figure 13 shows.’
      • ‘The traditional trefoil window arch expressed in timber is ubiquitous, along with corbelled timber dentils used as a supporting cornice.’


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