Definition 1 of 2
Definition
A condition inside a lead-acid battery in which lead sulfate crystals build up between the positive and negative plates and form a conductive path that partially or fully short-circuits the cell. A bridged cell loses voltage, will not hold a charge properly, and reduces the overall output of the battery.
Plain English
Inside a battery, unwanted material grows between the plates and connects them, causing the cell to leak its own charge and weaken the battery.
Context Anchor
Seen in aircraft electrical and avionics troubleshooting, especially when a meter or test unit is connected to a live circuit to read a signal.
Derivation
From the ordinary sense of a bridge connecting two separated things. In a battery the plates are meant to be electrically separated; when material grows across the gap it forms a 'bridge' between them, which is exactly what should not happen.
Why Pilots Care
A bridged cell quietly drains battery capacity and can leave the aircraft with less starting power or less emergency reserve than the gauge suggests. Recognising the symptom — a battery that will not hold a charge — leads to replacement before it causes a problem in flight.
Analogy
It is like looking through a window to see what is happening inside a room, instead of opening the door and changing what is happening in the room.
Intuition Check
Bridging does not mean building a physical bridge or simply jumping around a failed part. Here it means connecting across a circuit in a way that lets you read or use the signal with very little effect on that circuit.
Example Sentence 1
The mechanic suspected bridging in one of the cells after the battery repeatedly failed to hold a charge overnight.
Example Sentence 2
The finished part showed a resin-rich area where bridging had occurred, requiring a repair patch before the component could be returned to service.