Definition of fathom

• n. - A measure of length, containing six feet; the space to which a man can extend his arms; -- used chiefly in measuring cables, cordage, and the depth of navigable water by soundings.
• n. - The measure or extant of one's capacity; depth, as of intellect; profundity; reach; penetration.
• v. t. - To encompass with the arms extended or encircling; to measure by throwing the arms about; to span.
• v. t. - The measure by a sounding line; especially, to sound the depth of; to penetrate, measure, and comprehend; to get to the bottom of.