Antonyms of adj observable

1 sense of observable

Sense 1
discernible, evident, observable -- (capable of being seen or noticed; "a discernible change in attitude"; "a clearly evident erasure in the manuscript"; "an observable change in behavior")

INDIRECT (VIA noticeable) -> unnoticeable -- (not noticeable; not drawing attention; "her clothes were simple and unnoticeable"- J.G.Cozzens)

Similarity of adj observable

1 sense of observable

Sense 1
discernible, evident, observable -- (capable of being seen or noticed; "a discernible change in attitude"; "a clearly evident erasure in the manuscript"; "an observable change in behavior")
       => noticeable (vs. unnoticeable) -- (capable or worthy of being perceived; "noticeable shadows under her eyes"; "noticeable for its vivid historical background"; "a noticeable lack of friendliness")