IPA: /ˌʌnəʊbˈteɪnəbl/
KK: /ʌnəbˈteɪnəbl/
Not able to be obtained or reached.
The rare artifact was deemed unobtainable by the museum.
Unobtainable → It is formed from "un-" (meaning not), "ob-" (meaning toward), "tain" (from Latin "tenere", meaning to hold), and "-able" (meaning capable of). The word describes something that is not capable of being held or acquired.
Think of something that is 'not' ('un-') 'able' to be 'held' ('tenere') or 'acquired' — that's why unobtainable means it cannot be obtained.