fathom
noun
°(obsolete) Grasp, envelopment, control.
°(nautical) A measure of length corresponding to the outstretched arms, standardised to six feet, now used mainly for measuring depths in seas or oceans.
verb
°To encircle with outstretched arms, especially to take a measurement; to embrace.
°To measure the depth of, take a sounding of.
synonyms: fathom out, figure out, puzzle out, work out