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Webster 1828 Edition

Adj.

[in and retrievable, from retrieve.]

Not to be recovered or repaired; irrecoverable; irreparable; as an irretrievable loss.

irretrievable ‎(comparative more irretrievable, superlative most irretrievable)

irretrievable in The Century Dictionary, The Century Co., New York, 1911
irretrievable in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913