What is "chevrefoil"

"Chevrefoil" is a Breton lai by the medieval poet Marie de France. The eleventh poem in the collection called The Lais of Marie de France, its subject is an episode from the romance of Tristan and Iseult. The title means " honeysuckle," a symbol of love in the poem. "Chevrefoil" consists of 118 lines and survives in two manuscripts, Harley 978 or MS H, which contains all the Lais, and in Bibliothèque Nationale, nouv. acq. fr. 1104, or MS S.