Antonyms of adj protuberant

1 sense of protuberant

Sense 1
bellied, bellying, bulbous, bulging, bulgy, protuberant -- (curving outward)

INDIRECT (VIA protrusive) -> intrusive -- (thrusting inward; "an intrusive arm of the sea")

Similarity of adj protuberant

1 sense of protuberant

Sense 1
bellied, bellying, bulbous, bulging, bulgy, protuberant -- (curving outward)
       => protrusive (vs. intrusive) -- (thrusting outward)