black box

1 of 2

noun

1

: a usually complicated electronic device whose internal mechanism is usually hidden from or mysterious to the user

broadly : anything that has mysterious or unknown internal functions or mechanisms

2

: a crashworthy device in aircraft for recording cockpit conversations and flight data

3

: a device in an automobile that records information (such as speed, temperature, or gasoline efficiency) which can be used to monitor vehicle performance or determine a cause in the event of an accident

black box

2 of 2

adjective

: being or containing a warning of a serious or life-threatening side effect (such as stroke or muscle damage) that is highlighted by a black border on a prescription drug's label or accompanying literature

Examples of black box in a Sentence

Noun

The black boxes were recovered from the crash site and provided useful information about the cause of the crash.

Recent Examples on the Web

Noun

Investigators also encountered many issues extracting information from the vessel’s recorders, which are similar to black boxes on airplanes. —Alexandra Skores, CNN Money, 19 Nov. 2025

Safety concerns that led to the black box warnings, especially in regard to local vaginal estrogen, have turned out to be overblown. —Genevieve Hofmann, The Conversation, 18 Nov. 2025

Adjective

Doctors are less in agreement on the FDA’s decision to remove the black box warning from other forms of hormone therapy, which deliver estrogen systemically and may carry longer-term risks for some women. —Lisa Jarvis, Twin Cities, 23 Nov. 2025

Despite topical estrogen’s safety and effectiveness, the FDA did not distinguish between it and systemic estrogen when adding the black box warnings in 2003. —Genevieve Hofmann, The Conversation, 18 Nov. 2025

Word History

First Known Use

Noun

circa 1945, in the meaning defined at sense 1

Adjective

1968, in the meaning defined above

Rhymes for black box

• botox
• checkbox
• comox
• cornstalks
• cowpox
• crosswalks
• deadlocks
• detox
• feedstocks
• firebox
• gearbox
• hemlocks

Medical Definition

black box

adjective

: being or containing a warning of a serious or life-threatening side effect (as stroke, muscle damage, or suicidal tendencies) that is highlighted by a black border on a prescription drug's label or accompanying literature

A "black box" warning is the most serious warning placed in the labeling of a prescription medication.

—Johnathan D. Rockoff, The Fort Worth (Texas) Star-Telegram