Definition
A low point in a fuel tank, oil system, or fluid reservoir where water, sediment, and other contaminants collect by gravity, and from which they can be drained through a sampling or drain valve.
Plain English
The lowest spot in a tank or reservoir, where heavier stuff like water and dirt sinks and settles so it can be drained out before it causes trouble.
Context Anchor
Seen during aircraft maintenance, preflight fuel checks, and inspections of fuel, oil, and drain systems.
Derivation
From Middle English 'sumpe', meaning a swamp or low marshy place where water collects. The aviation use keeps that core idea: the lowest point where unwanted liquid gathers.
Why Pilots Care
Draining the sump removes water that could reach the engine and cause power loss or failure; undetected contamination is a common cause of in-flight engine stoppage.
Intuition Check
A sump is not the same as a pump. A sump collects fluid at a low point; a pump moves fluid from one place to another.
Example Sentence 1
During preflight, the pilot drained a small sample from each fuel sump and checked it for water and debris.
Example Sentence 2
During the annual inspection the mechanic cleaned the carburetor sump to remove accumulated sediment.