Definition
Protective electrical devices in an aircraft that automatically interrupt the flow of current to a circuit when the current exceeds a safe limit, preventing damage to wiring and components from overload or short circuits. Most aircraft circuit breakers can be reset manually after they trip (pop out), restoring power to the circuit if the underlying fault has cleared.
Plain English
Small switches that automatically shut off power to a part of the airplane's electrical system if too much current flows through it, protecting the wiring from overheating or starting a fire. Once the problem is gone, the pilot can usually push them back in to restore power.
Context Anchor
Seen during preflight checks of the cockpit electrical panel, and during flight if an electrical item stops working or a breaker has moved out of its normal position.
Derivation
From 'circuit' (a closed loop of electrical flow) and 'breaker' (something that breaks or interrupts). The name describes exactly what it does -- it breaks the circuit when needed.
Why Pilots Care
A tripped circuit breaker signals an electrical fault that could affect critical systems such as radios, instruments, lights, or fuel pumps; resetting without investigation risks fire or further damage.
Analogy
A circuit breaker is like a reusable safety shutoff in a house. It does not fix the problem that caused too much current; it only stops the power so the wiring is protected.
Intuition Check
Do not think of circuit breakers as normal on/off switches. If a breaker opens or moves out, treat it as a warning that something in that electrical path may be overloaded or faulty.
Example Sentence 1
During preflight, the pilot scanned the circuit breaker panel to confirm none were popped before applying power to the aircraft.
Example Sentence 2
After landing, the pilot reset the popped circuit breaker for the landing light once the short was repaired.