The Collaborative International Dictionary of English v.0.48:

Marattiaceae \Marattiaceae\ prop. n.
   The natural family of ferns coextensive with the order
   Marattiales, consisting of chiefly tropical eusporantiate
   ferns with gigantic fronds.

   Syn: family Marattiaceae.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Marattiaceae
    n 1: constituting the order Marattiales: chiefly tropical
         eusporangiate ferns with gigantic fronds [syn:
         Marattiaceae, family Marattiaceae]