Definition
Having two stable states. A bistable device or circuit can rest in either of two distinct conditions (such as on/off, set/reset, or high/low) and will remain in whichever state it was last placed until an input signal switches it to the other state.
Plain English
Something that has two settled positions and stays in whichever one it was last put into, until something changes it.
Context Anchor
Seen in descriptions of aircraft electrical systems, avionics, switches, relays, and indicator circuits.
Derivation
From Latin 'bi-' meaning two, and 'stable' meaning steady or unchanging. Literally 'two-steady' — two positions in which the device is content to rest.
Why Pilots Care
Bistable circuits are the building blocks of digital memory and many cockpit indicator and warning systems. They are how an avionics box 'remembers' a setting or a fault until reset.
Analogy
Like a light switch on the wall — it sits happily in either the up or down position and stays there until someone flips it.
Intuition Check
Bistable does not mean “extra stable.” It means “stable in either of two possible states.”
Example Sentence 1
The warning light is driven by a bistable circuit, so once it triggers it stays illuminated until the pilot presses the reset button.
Example Sentence 2
Technicians tested the bistable circuit to confirm it would flip states only when the correct voltage was applied.