The definition of culvert is a tunnel or a drain under a road or a railway that carries a stream or drainage from one side to the other.(noun)
A tunnel under the Reading Railroad that a stream flows through is an example of a culvert.
Culvert is defined as to channel or direct a stream or drainage through a tunnel under a road or railway.(verb)
When you build an enclosed tunnel under Reading Railroad to force a stream to pass underneath the railroad, this is an example of when you culvert the stream.
See culvert in Webster's New World College Dictionary
Origin: late 18th-c. < ?
See culvert in American Heritage Dictionary 4
Origin: Origin unknown.
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