unexchangeable: 1) негодный для обмена; не могущий быть замененным
Примеры
The instruction to be had in the Vorondadek schools is unexcelled even on Uversa. Образование, получаемое в школах Ворондадеков, остается непревзойденным даже на Уверсе.
He was especially famous at curing skin diseases, fainting-fits, mumps and the itch. At massage he was unexcelled; many were the men whom his hand had treated and who had found in it alleviation. Stomach-aches and the gripes he would often cure merely by massage. Особенно славился он как искусный врачеватель рожи, поносов, обмороков, свинки и чесотки.