Definition of trefoiled in English:

trefoiled

adjective

See trefoil

‘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.’
  • ‘There is a straight-armed cross with trefoiled terminals, with shears on the right and a stepped base.’
  • ‘This last, which is original, appears to have had a trefoiled head, but has been partly built up.’