n. Abbr. fth. or fm. A unit of length equal to 6 feet (1.83 meters), used principally in the measurement and specification of marine depths. tr.v. fath·omed, fath·om·ing, fath·oms 1. To penetrate to the meaning or nature of; comprehend. 2. To determine the depth of; sound. [Middle English fathme, from Old English fæthm, outstretched arms; see petə- in the Appendix of Indo-European roots.] fathom·a·ble adj. |
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