Antonyms of adj negligible

2 senses of negligible

Sense 1
negligible -- (so small as to be meaningless; insignificant; "the effect was negligible")

INDIRECT (VIA minimal, minimum) -> maximal, maximum -- (the greatest or most complete or best possible; "maximal expansion"; "maximum pressure")
INDIRECT (VIA minimal, minimum) -> maximal, maximum -- (the greatest or most complete or best possible; "maximal expansion"; "maximum pressure")

Sense 2
negligible, paltry, trifling -- (not worth considering; "he considered the prize too paltry for the lives it must cost"; "piffling efforts"; "a trifling matter")

INDIRECT (VIA worthless) -> valuable -- (having great material or monetary value especially for use or exchange; "a valuable diamond")

Similarity of adj negligible

2 senses of negligible

Sense 1
negligible -- (so small as to be meaningless; insignificant; "the effect was negligible")
       => minimal (vs. maximal), minimum (vs. maximum) -- (the least possible; "needed to enforce minimal standards"; "her grades were minimal"; "minimum wage"; "a minimal charge for the service")

Sense 2
negligible, paltry, trifling -- (not worth considering; "he considered the prize too paltry for the lives it must cost"; "piffling efforts"; "a trifling matter")
       => worthless (vs. valuable) -- (lacking in usefulness or value; "a worthless idler")