Plain English Meaning
A wind blowing sideways across your direction of travel, rather than straight at you or directly behind you. The word is also used for the short pattern leg flown sideways across the end of the runway after takeoff.
Full Definition
A wind that blows across the path of an aircraft, with a component perpendicular to the direction of flight or to the runway centerline. In traffic pattern usage, it also refers to the leg flown at right angles to the departure end of the runway.
Context Anchor
Commonly encountered in weather reports, takeoff and landing planning, runway selection, and pilot-controller .