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.

Fathom n. : The measure or extant of one's capacity; depth, as of intellect; profundity; reach; penetration.

Fathom v. t. : To encompass with the arms extended or encircling; to measure by throwing the arms about; to span.

Fathom 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.

Example:
What kind of person can Fathom to compare our President with Hitler?

Taxonomy
fathom, 100 fathoms, nautical charts, soundings, free encyclopedia, Ell, arms, measure, sounding line, setline, the Vitruvian Man, outstretched, thousandth, the United Kingdom, in Britain, depths, rope, groundline.

Defination from the web:
fathom is a unit of length in the Imperial system (and the derived U.S. customary units), used especially for measuring the depth of water. ... Until the 19th century in England, the length of the fathom was more variable: from 5½ feet on merchant vessels to either 5 feet or 7 feet ...