As a verb, it means to be carried along slowly by wind, water, or other forces, often without control or clear direction. As a noun, it can mean the general meaning of something, or a pile of snow or sand formed by the wind.
From Old English 'drift' meaning 'snowdrift, mass of driven snow', from 'drīfan' meaning 'to drive, push'. It originally referred to things driven together by wind or water. The idea of being carried along led to the modern sense of aimless movement.
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