Synonyms for impenetrable

Adjective

1. impenetrable (vs. penetrable), dense, thick

usage: not admitting of penetration or passage into or through; "an impenetrable fortress"; "impenetrable rain forests"

2. dense, heavy, impenetrable, thick (vs. thin)

usage: permitting little if any light to pass through because of denseness of matter; "dense smoke"; "heavy fog"; "impenetrable gloom"

3. impenetrable, incomprehensible (vs. comprehensible), uncomprehensible

usage: impossible to understand; "impenetrable jargon"