Definition
A small amount of reactive metal, typically barium or magnesium, sealed inside a vacuum tube or sealed electronic component to absorb residual gases and maintain the vacuum over the life of the device. The getter chemically combines with any stray gas molecules that leak in or are released from internal parts, keeping the inside of the tube clean and the vacuum intact.
Plain English
A tiny bit of special metal placed inside a sealed electronic tube to soak up any leftover gas, so the inside stays empty and the tube keeps working properly.
Context Anchor
Seen in aircraft electrical and avionics maintenance discussions, especially with older equipment that uses sealed electronic tubes.
Derivation
From the everyday English verb 'to get' -- the material literally 'gets' (captures) stray gas molecules. The name is descriptive of the job it does, which is why the term stuck in electronics.
Why Pilots Care
A getter helps a sealed electronic part keep working as designed. If air leaks in or the getter is used up, the part may become unreliable or fail.
Analogy
Think of it like the silica gel packet inside a new pair of shoes -- its only job is to quietly absorb stray moisture so the contents stay dry. The getter does the same thing inside a vacuum tube, but with gas molecules instead of water.
Intuition Check
Getter does not mean a person who gets something here. It means a material that captures unwanted gas inside a sealed electronic part.
Example Sentence 1
When the silvery coating of the getter inside a vacuum tube turns white, it means air has leaked in and the tube is no longer usable.
Example Sentence 2
Over years of service the getter continued to absorb trace gases released inside the gyro housing.