The measurement of distance in a straight line. (From the notion that crows always fly in a straight line.) From here to the office, it's about 20 miles as the crow flies, but it's more like 30 miles by car since you have to wind around the mountain.
If one place is a particular distance from another as the crow flies, the two places are that distance apart if you measure them in a straight line. I live at Mesa, Washington, about 10 miles as the crow flies from Hanford. This mountainous area has always been remote, although it is not far from Tehran as the crow flies. Note: People used to think that crows always travelled to their destination by the most direct route possible. `Make a beeline' is based on a similar idea.
used to refer to a shorter distance in a straight line across country rather than the distance as measured along a more circuitous road.
(informal) (of a distance) measured in a straight line: From here to the village it’s five miles as the crow flies, but it’s a lot further by road.