The Collaborative International Dictionary of English v.0.48:

White friar \White" fri`ar\ (Eccl.)
   A mendicant monk of the Carmelite order, so called from the
   white cloaks worn by the order. See Carmelite.
   [1913 Webster]

WordNet (r) 3.0 (2006):

White Friar
    n 1: a Roman Catholic friar wearing the white cloak of the
         Carmelite order; mendicant preachers [syn: Carmelite,
         White Friar]