Antonyms of adj intelligible

2 senses of intelligible

Sense 1
apprehensible, intelligible, graspable, perceivable, understandable -- (capable of being apprehended or understood)

INDIRECT (VIA comprehensible) -> incomprehensible, uncomprehensible -- (difficult to understand; "the most incomprehensible thing about the universe is that it is comprehensible"- A. Einstein)

Sense 2
intelligible (vs. unintelligible) -- (well articulated or enunciated, and loud enough to be heard distinctly; "intelligible pronunciation")

unintelligible (vs. intelligible) -- (poorly articulated or enunciated, or drowned by noise; "unintelligible speech")
        => slurred, thick -- (spoken as if with a thick tongue; "the thick speech of a drunkard"; "his words were slurred")

Similarity of adj intelligible

2 senses of intelligible

Sense 1
apprehensible, intelligible, graspable, perceivable, understandable -- (capable of being apprehended or understood)
       => comprehensible (vs. incomprehensible), comprehendible -- (capable of being comprehended or understood; "an idea comprehensible to the average mind")

Sense 2
intelligible (vs. unintelligible) -- (well articulated or enunciated, and loud enough to be heard distinctly; "intelligible pronunciation")
          Also See-> comprehensible#1, comprehendible#1