indefinable
adjective
[ ɪndɪˈfʌɪnəb(ə)l ]
• not able to be defined or described exactly.
• "she reminds me, in some indefinable way, of my grandmother"
Similar:
hard to define,
hard to describe,
indescribable,
inexpressible,
nameless,
vague,
obscure,
indefinite,
unanalysable,
intangible,
impalpable,
incorporeal,
elusive,
fugitive,
