altocumulus

from WordNet (r) 3.0 (2006)

altocumulus
    n 1: a cumulus cloud at an intermediate altitude of 2 or 3 miles
         [syn: {altocumulus}, {altocumulus cloud}]

from The Collaborative International Dictionary of English v.0.48

Alto-cumulus \Al`to-cu"mu*lus\, n. [L. altus high + L. & E.
   cumulus.] (Meteor.)
   A fleecy cloud formation consisting of large whitish or
   grayish globular cloudlets with shaded portions, often
   grouped in flocks or rows.
   [Webster 1913 Suppl.]