The quality of being fathomable.

Very deep (especially of water deeper than a lead line can measure); bottomless. / (by extension) unfathomable or incomprehensible.

(nautical) A depth finder that uses sound waves to determine the depth of water.

plural of fathometer

The state or condition of being fathomless.

In a fathomless manner, to a fathomless degree.

(rare, nonstandard) Very deep; abyssal.

(rare, nonstandard) Profoundly; deeply.

plural of fathomage

(mining) The amount of money paid to a miner based on fathoms of material worked.