fathom

nouns

a linear unit of measurement (equal to 6 feet) for water depth
fathom, fthm
(mining) a unit of volume (equal to 6 cubic feet) used in measuring bodies of ore
fathom, fthm

verbs

come to understand
bottom, fathom, penetrate
measure the depth of (a body of water) with a sounding line
fathom, sound