Definition of "air mass"

air mass

/ˈɛː mas/

noun
plural air masses
1. (meteorology) A particular volume of air, especially one having a roughly uniform temperature, pressure and water vapour content.
  Quotations
  After a 227-day drought ending with December temperatures above 90, a polar air mass collided with a wave of damp tropical air, condensed it in seven days of cloudburst.
  1939 January 2, “Cloudburst”, in Time
  The mercury has been soaring in the state since the weekend because of an air mass hovering over Queensland.
  2013 December 31, Bridie Jabour, The Guardian