Real Dictionary

monsoon
countable noun: The monsoon is the season in Southern Asia when there is a lot of very heavy rain.

monsoon in American English
a seasonal wind of the Indian Ocean and S Asia, blowing from the southwest from April to October, and from the northeast during the rest of the year
noun: the seasonal wind of the Indian Ocean and southern Asia, blowing from the southwest in summer and from the northeast in winter

monsoon in British English
noun: a seasonal wind of S Asia that blows from the southwest in summer, bringing heavy rains, and from the northeast in winter