adj. 25B6; adjective UNABLE TO BE SEEN, not visible; undetectable, indiscernible, inconspicuous, imperceptible; unseen, unnoticed, unobserved, hidden, obscured, out of sight.
INVISIBLE
Meaning of INVISIBLE in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012