Antonyms of adj impenetrable

3 senses of impenetrable

Sense 1
impenetrable (vs. penetrable) -- (not admitting of penetration or passage into or through; "an impenetrable fortress"; "impenetrable rain forests")

penetrable (vs. impenetrable) -- (admitting of penetration or passage into or through; "a penetrable wall"; "penetrable defenses")

Sense 2
dense, heavy, impenetrable -- (permitting little if any light to pass through because of denseness of matter; "dense smoke"; "heavy fog"; "impenetrable gloom")

INDIRECT (VIA thick) -> thin -- (relatively thin in consistency or low in density; not viscous; "air is thin at high altitudes"; "a thin soup"; "skimmed milk is much thinner than whole milk"; "thin oil")

Sense 3
impenetrable -- (impossible to understand; "impenetrable jargon")

INDIRECT (VIA incomprehensible) -> comprehensible, comprehendible -- (capable of being comprehended or understood; "an idea comprehensible to the average mind")

Similarity of adj impenetrable

3 senses of impenetrable

Sense 1
impenetrable (vs. penetrable) -- (not admitting of penetration or passage into or through; "an impenetrable fortress"; "impenetrable rain forests")
       => dense, thick -- (hard to pass through because of dense growth; "dense vegetation"; "thick woods")

Sense 2
dense, heavy, impenetrable -- (permitting little if any light to pass through because of denseness of matter; "dense smoke"; "heavy fog"; "impenetrable gloom")
       => thick (vs. thin) -- (relatively dense in consistency; "thick cream"; "thick soup"; "thick smoke"; "thick fog")

Sense 3
impenetrable -- (impossible to understand; "impenetrable jargon")
       => incomprehensible (vs. comprehensible), uncomprehensible -- (difficult to understand; "the most incomprehensible thing about the universe is that it is comprehensible"- A. Einstein)