Definition of unreplaceable in English:
unreplaceable
adjective (ˌ)ʌnriːˈpleɪsəbl(ˌ)ʌnrɪˈpleɪsəbl
That cannot be replaced; irreplaceable.
Origin
Early 19th century; earliest use found in Robert Southey (1774–1843), poet and reviewer. From un- + replaceable.