fathom - Dictionary Definition : Vocabulary.com

To fathom something is to understand it thoroughly, and is usually used in the negative, as in "I can't fathom why he doesn't want to go along with us."

Fathom is from Middle English fadme, from Old English fæthm "outstretched arms." The Old English and modern English noun also refers to a unit of length used to measure the depth of water. To understand something thoroughly is "to get to the bottom of it."

PRIMARY MEANINGS OF: fathom

1	n v	a linear unit of measurement (equal to 6 feet) for water depth measure the depth of (a body of water) with a sounding line
2	v	come to understand

FULL DEFINITIONS OF: fathom

1

n a linear unit of measurement (equal to 6 feet) for water depth

Synonyms:: fthm

Type of:: linear measure, linear unit
a unit of measurement of length

n (mining) a unit of volume (equal to 6 cubic feet) used in measuring bodies of ore

Synonyms:: fthm

Type of:: capacity measure, capacity unit, cubage unit, cubature unit, cubic content unit, cubic measure, displacement unit, volume unit
a unit of measurement of volume or capacity

v measure the depth of (a body of water) with a sounding line

Synonyms:: sound

Type of:: measure, quantify
express as a number or measure or quantity

2

v come to understand

Synonyms:: bottom, penetrate

Type of:: understand
know and comprehend the nature or meaning of