noun · 3 senses · updated from the 2026-07-25 local source snapshot
Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.
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UK:/ˈɛː mas/
US:/ɛəɹ mæs/
US:/ɛːɹ mæs/
1
noun
Meaning 1
a widespread body of air, the properties of which can be identified as: (a) having been established while that air was situated over a particular region of the Earth's surface (airmass source region) and (b) undergoing specific modifications while in transit away from the source region. An air mass is often defined as a widespread body of air that is approximately homogeneous in its horizontal extent, particularly with reference to temperature and moisture distribution; in addition, the vertical temperature and moisture variations are approximately the same over its horizontal extent.
Definition source: English Wiktionary via Wiktextract
