To cross or traverse something sideways; to pass across (e.g., a road, a field, or a room).
子どもが急に車道を横切ったので驚いた。
I was startled because a child suddenly crossed the roadway.
猫が庭を横切って塀の上に乗った。
A cat crossed the garden and jumped onto the fence.
午前の光が部屋を横切って差し込んだ。
The morning light streamed across the room.