fail closed

verb

Of an access control system: to automatically block all traffic in the case of a failure. For example, an electronic safe becoming impossible to unlock in the event of a power outage.

“Coordinate term: fail open”

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Meanings

verbfail closed (third-person singular simple present fails closed, present participle failing closed, simple past and past participle failed closed)

present singular third person fails closed · participle present failing closed · participle past failed closed · past failed closed

  1. Of an access control system: to automatically block all traffic in the case of a failure. For example, an electronic safe becoming impossible to unlock in the event of a power outage.

    Coordinate term: fail open

Cite this entry
APA

fail closed. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/fail%20closed

MLA

“fail closed.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/fail%20closed. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “fail closed,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/fail%20closed.

Source: fail closed on Wiktionary, CC BY-SA 4.0.