Source : Webster's Revised Unabridged Dictionary (1913)

Air cooling \Air cooling\
   In gasoline-engine motor vehicles, the cooling of the
   cylinder by increasing its radiating surface by means of ribs
   or radiators, and placing it so that it is exposed to a
   current of air. Cf. {Water cooling}. -- {Air"-cooled`}, a.

Source : WordNet®

air-cooled
     adj : cooled by a flow of air; "an air-cooled engine"