Nonpenetrable

Part of speech: adjective

Definitions

1. Not allowing passage or entry through its surface or substance; incapable of being pierced, entered, or penetrated physically or figuratively; resistant to influence, understanding, or access
2. Impermeable to movement or intrusion from outside; unable to be breached or penetrated by materials, forces, or ideas; characterizing something sealed off or impenetrable to perception or communication
3. Resistant to passage or infiltration in a physical or abstract sense; forbidding entrance or penetration by blocking or deflecting attempts; describing something impervious to external forces or comprehension

Etymology: "Nonpenetrable" is a plain formation: the prefix "non-", meaning "not," attached to "penetrable," which itself comes from "penetrate." That verb traces back to Latin "penetrare," meaning "to enter into, to get inside," built from "penitus," "inward" or "deep within." So the core idea is of getting deep inside something, and "penetrable" describes a thing that can be entered that way. The prefix "non-" comes straight from Latin "non," "not," and has been used freely in English to create negative adjectives from existing words. "Nonpenetrable" therefore needs no special history of its own: it simply reverses the sense of "penetrable," describing something that cannot be pierced or entered. Its meaning is fully transparent from its parts, which is why it appears in technical and everyday contexts alike, from armor and walls to membranes and materials.

Synonyms: impenetrable, impermeable, inaccessible, invulnerable, sealed

Antonyms: penetrable, permeable, accessible, vulnerable, porous