Definition
A cone with its tip cut off by a plane parallel to its base, leaving a shape with two circular ends of different diameters joined by a sloping side.
Plain English
A cone shape with the pointed top sliced off flat, so it has a small round top and a larger round bottom.
Context Anchor
Seen in aircraft drawings, sheet-metal layout, and descriptions of tapered parts such as fairings, ducts, or cowling sections.
Derivation
From the Latin truncare, meaning 'to cut off' or 'to lop'. The same root gives us 'trunk' (a tree with its branches cut). A truncated cone is literally a cone that has been cut off.
Why Pilots Care
A pilot may not use this term in normal cockpit conversation, but understanding it helps when reading maintenance descriptions, aircraft construction material, or diagrams of tapered airplane parts.
Analogy
Think of a paper drinking cup or a flowerpot — wider at one end, narrower at the other, with both ends open and flat.
Intuition Check
Do not think of “truncated” as just meaning “short.” Here it means the cone has been cut off, leaving a smaller flat circular end instead of a point.
Example Sentence 1
The tailpipe of the turbine engine is shaped like a truncated cone to help direct exhaust gases.
Example Sentence 2
Technicians examined the truncated cone section of the exhaust nozzle for cracks after the flight.