The Collaborative International Dictionary of English v.0.48:

Nebuly \Neb"u*ly\, n. (Her. & Arch.)
   A line or a decoration composed of successive short curves or
   waves supposed to resemble a cloud. See N['e]bul['e]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

N'ebul'e \N['e]`bu`l['e]"\, Nebuly \Neb"u*ly\, a. [F.
   n['e]bul['e].] (Her.)
   Composed of successive short curves supposed to resemble a
   cloud; -- said of a heraldic line by which an ordinary or
   subordinary may be bounded.
   [1913 Webster]