Impossible to sound; whose depth cannot be gauged.(adjective)
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Use "unsoundable" in a sentence
"Before undertaking to fathom with the plummet of logic the unsoundable mystery of foreknowledge, let us see what we can know through a return to the real nature of man as he is, and especially to the real nature of the new Adam who is Christ, the Son of"
"God fully revealed; that the Divine Spirit, incarnate in Him, comes upon men still and brings them into the bottomless, unsoundable deeps of Life with God, and makes it possible for them to attain a perfect life; that the Scriptures as outward and legal must be transcended, and that they must be spiritually discerned and experienced."
"There shall be a depth of silence in thee, deeper than this sea, which is but ten miles deep: a silence unsoundable; known to God only."