n. & v.
n. (pl. often fathom when prec. by a number) 1 a measure of six feet, esp. used in taking depth soundings. 2 Brit. a quantity of wood six feet square in cross-section.
v.tr. 1 grasp or comprehend (a problem or difficulty). 2 measure the depth of (water) with a sounding-line. fathomable adj. fathomless adj.
[ OE fthm outstretched arms f. Gmc ]