verb
fathom
FATH-um/ˈfæðəm/
To understand something difficult or mysterious.
The older man finally fathoms how the puzzle's interlocking pieces fit together.

Etymology
The verb originally meant “to embrace or surround” and later meant taking soundings to measure depth. Understanding something became figuratively getting to its bottom with the mind.
In context
she had now sought me--to beseech me to relinquish my efforts to fathom the mystery of the death of Edward Craig.
More examples
- She struggles to fathom the scale of the universe.
- We finally fathomed what the poet meant.
- His reasons for quitting are hard to fathom.
Forms
fathom · fathoms · fathomed · fathoming
fathomable adjective — Capable of being understood or explained.
unfathomable adjective — Impossible to understand or explain fully.
Similar words
- understand
- Broader; does not imply that something is difficult or mysterious.
- grasp
- Emphasizes achieving a clear understanding, sometimes quite suddenly.
- comprehend
- Often emphasizes understanding the full meaning or complexity.