Plain English Meaning
A tiny dot in the middle of the little airplane symbol on your attitude indicator. You use it as a fine pointer to judge exactly how much the nose is pitched up or down compared to the horizon line.
Full Definition
A small reference mark on the center of the attitude indicator's miniature airplane, used as a precise pitch reference point against the artificial horizon line during instrument flight.
Context Anchor
Seen on analog attitude indicators during instrument flying, especially when setting or holding pitch.
Derivation
Fuselage comes from a French word meaning shaped like a spindle, and in it means the main of the airplane. Dot means a small mark. Together, fuselage dot means the small mark that stands for the airplane’s body on the attitude indicator.