The Collaborative International Dictionary of English v.0.48:

Hydrangeaceae \Hydrangeaceae\ prop. n.
   A natural family of plants including the hydrangeas,
   sometimes included in the family Saxifragaceae.

   Syn: family Hydrangeaceae, hydrangea family.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Hydrangeaceae
    n 1: sometimes included in the family Saxifragaceae [syn:
         Hydrangeaceae, family Hydrangeaceae, hydrangea
         family]