/ ˌmɒnˈsuːn; NAmE ˌmɑːn-/ noun
1.
a period of heavy rain in summer in S Asia; the rain that falls during this period
2.
a wind in S Asia that blows from the south-west in summer, bringing rain, and the north-east in winter
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WORD ORIGIN
late 16th cent.: from Portuguese monção , from Arabic mawsim season, from wasama to mark, brand.