impenetrable

adjectives

not admitting of penetration or passage into or through
"an impenetrable fortress"; "impenetrable rain forests"
impenetrable
is derived from
impenetrability
antonym
penetrable
is similar to
hard to pass through because of dense growth
"dense vegetation"; "thick woods"
dense, thick
permitting little if any light to pass through because of denseness of matter
"dense smoke"; "heavy fog"; "impenetrable gloom"
dense, heavy, impenetrable
impossible to understand
"impenetrable jargon"
impenetrable
is derived from
impenetrableness
is similar to
difficult to understand
"the most incomprehensible thing about the universe is that it is comprehensible"- A. Einstein
incomprehensible, uncomprehensible