Pronunciation: (fa&thslash;'um), [key]
—n., pl. fath•oms, (esp. collectively) fath•om,
a unit of length equal to six feet (1.8 meters): used chiefly in nautical measurements. Abbr.: fath
1. to measure the depth of by means of a sounding line; sound.
2. to penetrate to the truth of; comprehend; understand: to fathom someone's motives.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.