Antonyms of adj insignificant

4 senses of insignificant

Sense 1
insignificant, undistinguished -- (not worthy of notice)

INDIRECT (VIA unnoticeable) -> noticeable -- (capable or worthy of being perceived; "noticeable shadows under her eyes"; "noticeable for its vivid historical background"; "a noticeable lack of friendliness")

Sense 2
insignificant -- (signifying nothing; "insignificant sounds")

INDIRECT (VIA meaningless) -> meaningful -- (having a meaning or purpose; "a meaningful explanation"; "a meaningful discussion"; "a meaningful pause")

Sense 3
insignificant, peanut -- (of little importance or influence or power; of minor status; "a minor, insignificant bureaucrat"; "peanut politicians")

INDIRECT (VIA minor) -> major -- (of greater importance or stature or rank; "a major artist"; "a major role"; "major highways")

Sense 4
insignificant (vs. significant), unimportant -- (devoid of importance, meaning, or force)

significant (vs. insignificant), important -- (important in effect or meaning; "a significant change in tax laws"; "a significant change in the Constitution"; "a significant contribution"; "significant details"; "statistically significant")
        => momentous -- (of very great significance; "deciding to drop the atom bomb was a very big decision"; "a momentous event")
        => epochal, epoch-making -- (highly significant or important especially bringing about or marking the beginning of a new development or era; "epochal decisions made by Roosevelt and Churchill"; "an epoch-making discovery")
        => earthshaking, world-shaking, world-shattering -- (sufficiently significant to affect the whole world; "earthshaking proposals"; "the contest was no world-shaking affair"; "the conversation...could hardly be called world-shattering")
        => evidential, evidentiary -- (serving as or based on evidence; "evidential signs of a forced entry"; "its evidentiary value")
        => fundamental, profound -- (far-reaching and thoroughgoing in effect especially on the nature of something; "the fundamental revolution in human values that has occurred"; "the book underwent fundamental changes"; "committed the fundamental error of confusing spending with extravagance"; "profound social changes")
        => large -- (fairly large or important in effect; influential; "played a large role in the negotiations")
        => monumental -- (of outstanding significance; "Einstein's monumental contributions to physics")
        => noteworthy, remarkable -- (worthy of notice; "a noteworthy fact is that her students rarely complain"; "a remarkable achievement")
        => probative, probatory -- (tending to prove a particular proposition or to persuade you of the truth of an allegation; "evidence should only be excluded if its probative value was outweighed by its prejudicial effect")
        => operative -- (effective; producing a desired effect; "the operative word")
        => portentous, prodigious -- (of momentous or ominous significance; "such a portentous...monster raised all my curiosity"- Herman Melville; "a prodigious vision")

Similarity of adj insignificant

4 senses of insignificant

Sense 1
insignificant, undistinguished -- (not worthy of notice)
       => unnoticeable (vs. noticeable) -- (not noticeable; not drawing attention; "her clothes were simple and unnoticeable"- J.G.Cozzens)

Sense 2
insignificant -- (signifying nothing; "insignificant sounds")
       => meaningless (vs. meaningful), nonmeaningful -- (having no meaning or direction or purpose; "a meaningless endeavor"; "a meaningless life"; "a verbose but meaningless explanation")

Sense 3
insignificant, peanut -- (of little importance or influence or power; of minor status; "a minor, insignificant bureaucrat"; "peanut politicians")
       => minor (vs. major) -- (of lesser importance or stature or rank; "a minor poet"; "had a minor part in the play"; "a minor official"; "many of these hardy adventurers were minor noblemen"; "minor back roads")

Sense 4
insignificant (vs. significant), unimportant -- (devoid of importance, meaning, or force)
       => hole-and-corner, hole-in-corner -- (relating to the peripheral and unimportant aspects of life; "a hole-and-corner life in some obscure community"- H.G.Wells)
       => flimsy, fragile, slight, tenuous, thin -- (lacking substance or significance; "slight evidence"; "a tenuous argument"; "a thin plot"; a fragile claim to fame")
       => inappreciable -- (too small to make a significant difference; "inappreciable fluctuations in temperature")
       => light -- (having little importance; "losing his job was no light matter")
       => superficial, trivial -- (of little substance or significance; "a few superficial editorial changes"; "only trivial objections")
          Also See-> meaningless#1, nonmeaningful#1; unimportant#1