unregainable
/(ˌ)ʌnrɪˈɡeɪnəbl/ /(ˌ)ʌnriːˈɡeɪnəbl/adjective
That cannot be regained; irrecoverable.
noun
With the. That which cannot be regained or recovered.
Origin
Mid 17th century; earliest use found in Thomas Palmer (?1541–1626), author. From un- + regain + -able.