"science of the earth's atmosphere, scientific study of weather and climate," especially with a view to forecasting the weather, 1610s, from French météorologie and directly from Greek meteōrologia "treatise on celestial phenomena," literally "discussion of high things," from meteōron "thing high up" (see meteor) + -logia "treatment of" (see -logy).
word-forming element meaning "one who does or makes," also used to indicate adherence to a certain doctrine or custom, from French -iste and directly from Latin -ista (source also of Spanish, Portuguese, Italian -ista), from Greek agent-noun ending -istes, which is from -is-, ending of the stem of verbs in -izein, + agential suffix -tes.
Variant -ister (as in chorister, barrister) is from Old French -istre, on false analogy of ministre. Variant -ista is from Spanish, popularized in American English 1970s by names of Latin-American revolutionary movements.
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Definitions of meteorologist from WordNet
a specialist who studies processes in the earth's atmosphere that cause weather conditions;