What term describes something that is completely sealed and impervious to outside influence?

The term "hermetic" refers to something that is completely sealed off from outside influence, often implying that it is airtight or impervious to external elements. This term has its roots in Hermeticism, which is related to ancient beliefs in alchemy and the mystical writings attributed to Hermes Trismegistus. In modern usage, "hermetic" conveys the idea of a closure that protects its contents from contamination or external factors, making it particularly applicable in contexts like chemistry or food storage, where maintaining purity is crucial.

The other terms do not carry the same meaning. "Hew" refers to cutting or shaping something, typically wood, and does not invoke any idea of sealing or protection. "Hirsute" pertains to having a lot of hair, which is unrelated to the concept of being sealed. "Improvident" describes a lack of foresight or planning, particularly in financial matters, and has no connection to the idea of being impervious or sealed off. Thus, "hermetic" is the appropriate term for something that is fully enclosed and impervious to outside influence.