The Collaborative International Dictionary of English v.0.48:

Maigre \Mai"gre\, a. [F. See Meager.]
   Belonging to a fast day or fast; as, a maigre day. --Walpole.
   [1913 Webster]

   Maigre food (R. C. Ch.), food allowed to be eaten on fast
      days.
      [1913 Webster]