IPA: /ˌʌnəˈdɒptəbl/
KK: /ʌnəˈdɑptəbl/
Something that cannot be adopted or is not suitable for adoption.
The shelter has many pets, but some are considered unadoptable due to their health issues.
Unadoptable → It is formed from "un-" (meaning not) and "adoptable" (from Latin "adoptare", meaning to choose for oneself). The word "unadoptable" means not able to be chosen or taken in as an adoptive child.
Think of 'not' ('un-') being added to 'able to be chosen' ('adoptable') — that's why unadoptable means something that cannot be chosen for adoption.