English
Adjective
unconvertible (comparative more unconvertible, superlative most unconvertible)
-  That cannot be converted.
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1916,  James Marchant,  Alfred Russel Wallace= Letters and Reminiscences, Vol. 1 (of 2):- I can only recommend you to read again Darwin's account of the horse family and its comparison with pigeons; and if that does not convince and stagger you, then you are unconvertible.
 
 
 
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1922,  Francesco Saverio Nitti,  Peaceless Europe:- If the situation created by the War has transformed also the English circulation into unconvertible paper money, this is merely a passing fact.