The Collaborative International Dictionary of English v.0.48:

Air hole \Air" hole`\ ([^a]r" h[=o]l`).
   1. A hole to admit or discharge air; specifically, a spot in
      the ice not frozen over.
      [1913 Webster]

   2. (Founding) A fault in a casting, produced by a bubble of
      air; a blowhole.
      [1913 Webster]

   3. (A["e]ronautics) A local region in the atmosphere having a
      downward movement and offering less than normal support
      for the sustaining surfaces of a flying machine, causing
      an airplane to drop suddenly. Same as air pocket.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Air pocket \Air" pock"et\ (p[o^]k"[e^]t). (aeronautics)
   A local region in the atmosphere having a downward movement
   and offering less than normal support for the sustaining
   surfaces of a flying machine, causing an airplane to drop
   suddenly. Same as air hole.
   [PJC.]

WordNet (r) 3.0 (2006):

air hole
    n 1: a local region of low pressure or descending air that
         causes a plane to lose height suddenly [syn: air pocket,
         pocket, air hole]
    2: a hole that allows the passage of air