divining rod

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A forked branch or stick that is believed to indicate subterranean water or minerals by bending downward when held over a source.

Century Dictionary and Cyclopedia

1. n. A rod or twig used in divining; especially, a twig, generally of hazel, held in the hand and supposed by its bending downward to indicate spots where metalliferous deposits or water may be found by digging. It is usually made of two twigs of hazel, or of apple or some other fruit-tree, tied together at the top with thread, or of a naturally forked branch, and is grasped by both hands in such a way that it moves when attracted by the sought-for deposit. This method of searching for ore or water has been in use for centuries, but its efficacy is now rarely credited by intelligent persons.

Wiktionary

1. n. rod used for dowsing, a technique of divination used to locate subterranean sources of water, metal, other mineral resources or even various other things through magic, or according to many believers a natural phenomenon

GNU Webster's 1913

1. adj. a rod, commonly of witch hazel, with forked branches, used by those who claim to be able to discover water or metals under ground by sensing them through such a rod.

WordNet 3.0

1. n. forked stick that is said to dip down to indicate underground water or oil