Plain English Meaning
A landing gear setup with two wheels under the middle of the airplane and one wheel under the nose, so the airplane sits level on the ground.
Full Definition
A landing gear arrangement with two main wheels positioned aft of the airplane's center of gravity and a single nose wheel forward of it. The nose wheel may be steerable, free-castering, or fixed, and supports the forward fuselage on the ground.
Context Anchor
Seen when learning about airplane landing gear types, especially how an airplane sits, steers, taxis, takes off, and lands on the ground.
Derivation
From the Greek 'tri' (three) plus 'cycle' (wheel) -- literally 'three-wheeler.' The name comes from the child's tricycle, which has the same wheel layout: one in front, two in back.
Why Pilots Care
Tricycle gear improves forward during and is more forgiving on than conventional , reducing the chance of a .