fathom
1. fath.om \'fath-*m\ n [ME fadme, fr. OE fthm outstretched arms, length of the ou]tstretched arms; akin to ON fathmr fathom, L pate-re to be open, pandere to spread out, Gk petannynai 1: a unit of length equal to 6 feet used esp. for measuring the depth of wa ter 2: COMPREHENSION 2. fathom \'fath-*-m*-b*l\ vt 1: to measure by a sounding line 2: to penetrate and come to understand : to take soundings; also : PROBE - fath.om.able aj