unsoundable

/ʌnˈsaʊndəbəl/
adjective
  1. Too deep to measure; impossible to fathom or understand fully.
    • The mystery of the ancient ruins seemed unsoundable to the archaeologists.
    • The ocean in that region is unsoundable, even with modern equipment.
    • Her grief was unsoundable, a depth no one could reach.
Antonyms
What does "unsoundable" mean? | whatsthatwordmean | whatsthatwordmean