fathom

To understand something difficult or confusing, especially someone's reasons or behaviour.

• I cannot fathom his reasons.
• She finally fathomed out the strange message.
• Can anyone fathom why the machine keeps stopping?

How to use it: fathom why/how/what… (I cannot fathom why he left so suddenly.); fathom something out (Can you fathom this puzzle out?)

Similar words: understand, figure out, comprehend

Common phrases: fathom something out, fathom someone's motives, cannot fathom why

To measure how deep water is.

• The sailors fathomed the bay.
• They used a weighted rope to fathom the water.
• We must fathom the channel before the ship enters.

Similar words: sound

Common phrases: fathom the depth, fathom the bay, fathom the channel

A unit of length equal to six feet, used especially to measure water depth.

• The water is one fathom deep.
• We anchored in six fathoms of water.
• The chart gives all depths in fathoms.

Common phrases: a fathom deep, one fathom, fathom of rope

A measure of distance from shore based on the water depth at the nearest point of that depth.

• The boat lay a fathom offshore.
• They waited two fathoms from shore, where the water reached that depth.
• We rowed three fathoms out, stopping at the nearest three-fathom depth.

Common phrases: a fathom offshore, a fathom out