Definition
A small indicator light on an instrument panel used to alert the pilot to a specific condition, such as a system status, a caution, or a setting that has been reached. The term refers to the light itself, which is typically a small, low-intensity bulb mounted near or on the instrument it relates to.
Plain English
A tiny warning or indicator light on the panel that tells the pilot something specific has happened or that a setting has been met.
Context Anchor
Seen in aircraft cockpit lighting and maintenance discussions, especially when checking instrument lights before night flight.
Derivation
The name comes from the small size of the light — about the size of a bug. It is informal shop language that stuck because it is descriptive: a tiny glowing point on the panel.
Why Pilots Care
Provides immediate visual alert to a problem so the pilot can take corrective action before it becomes serious.
Analogy
It is like a tiny reading lamp aimed at one gauge instead of a room light that brightens everything.
Intuition Check
Do not read “bug light” as a light for a selected heading or speed bug. Here it means a small light used to illuminate an instrument face.
Example Sentence 1
The bug light next to the gear selector came on, confirming the gear was in transit.
Example Sentence 2
Before takeoff I scanned the panel and confirmed no bug lights were illuminated.