Definition
An adjustment of small auxiliary surfaces (trim tabs) or equivalent mechanisms on the elevator, rudder, or ailerons that relieves continuous control pressure required from the pilot, allowing the airplane to maintain a desired attitude or flight condition without sustained input on the controls.
Plain English
Trim is a way to set the controls so the airplane holds its current pitch, yaw, or roll on its own, so the pilot doesn't have to keep pushing or pulling on the yoke or rudder pedals.
Context Anchor
Seen on the before-takeoff checklist, often as “Trim — set for takeoff.”
Derivation
From the nautical term 'trim,' meaning to adjust a vessel's balance — for example, by shifting cargo so the boat sits level in the water. In aviation, trim plays the same role: balancing the airplane's controls so it flies steadily without constant correction.
Why Pilots Care
Correct trim reduces control forces, lowers pilot workload, prevents fatigue on longer flights, and keeps the aircraft stable if attention is briefly diverted.
Intuition Check
Trim does not mean making something neat or decorative here. It means adjusting the airplane so the pilot does not have to hold constant pressure on the controls.
Example Sentence 1
After leveling off at cruise altitude, the pilot adjusted the trim until the airplane held its pitch with no pressure on the yoke.
Example Sentence 2
After leveling at cruise altitude the pilot rolled the trim wheel forward until yoke pressure disappeared.