Antonyms of adj unchallengeable

1 sense of unchallengeable

Sense 1
unchallengeable -- (not open to challenge; "unchallengeable facts"; "a position of unchallengeable supremacy")

INDIRECT (VIA uncontroversial) -> controversial -- (marked by or capable of arousing controversy; "the issue of the death penalty is highly controversial"; "Rushdie's controversial book"; "a controversial decision on affirmative action")

Similarity of adj unchallengeable

1 sense of unchallengeable

Sense 1
unchallengeable -- (not open to challenge; "unchallengeable facts"; "a position of unchallengeable supremacy")
       => uncontroversial (vs. controversial), noncontroversial -- (not likely to arouse controversy)