monsoon

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A wind system that influences large climatic regions and reverses direction seasonally.
2. n. A wind from the southwest or south that brings heavy rainfall to southern Asia in the summer.
3. n. The rain that accompanies this wind.

Century Dictionary and Cyclopedia

1. n. A wind occurring in the alternation of the trade-winds in India and the north Indian ocean. During the half-year from April to October the regular northeast trade-winds are reversed, and, with occasional interruptions, the wind blows almost a steady gale from the southwest. In some places the change of the monsoons is attended with calms; in others with variable winds; and in others, as in China, with storms and much rain. These tempests seamen call the breaking up of the monsoon. The reversed trade-wind is termed the summer, southwest, or wet monsoon, and the trade-wind is termed the winter, northeast, or dry monsoon.
2. n. Any of the winds that have annual alternations of direction and velocity, arising from differences of temperature between continents or islands and the surrounding ocean.

Wiktionary

1. n. Any of a number of winds associated with regions where most rain falls during a particular season.
2. n. Tropical rainy season when the rain lasts for several months with few interruptions.
3. n. The rains themselves.
4. n. Entire meteorological systems with such characteristics.

GNU Webster's 1913

1. n. A wind blowing part of the year from one direction, alternating with a wind from the opposite direction; -- a term applied particularly to periodical winds of the Indian Ocean, which blow from the southwest from the latter part of May to the middle of September, and from the northeast from about the middle of October to the middle of December.
2. n. A heavy rainfall in India associated with the southwest monsoon{1}.
3. n. The season in which the monsoon{2} occurs.

WordNet 3.0

1. n. rainy season in southern Asia when the southwestern monsoon blows, bringing heavy rains
2. n. a seasonal wind in southern Asia; blows from the southwest (bringing rain) in summer and from the northeast in winter
3. n. any wind that changes direction with the seasons