[fath.om] n [ME fadme, fr. OE faethm outstretched arms, length of the outstretched arms; akin to ON fathmr fathom, L patere to be open, pandere to spread out, Gk petannynai] (bef. 12c) 1: a unit of length equal to six feet (1.83 meters) used esp. for measuring the depth of water
2: comprehension
[2]fathom vi (1607) 1: probe
2: to take soundings ~ vt 1: to measure by a sounding line
2: to penetrate and come to understand "couldn't ~ the problem" -- fath.om.able adj