Definition
Visible returns on a radar display caused by precipitation, terrain, ground objects, sea state, or other unwanted reflections that obscure or interfere with the targets the controller or pilot is trying to see.
Plain English
Extra blips and shading on a radar screen caused by things like rain, hills, or buildings, which make it harder to pick out the actual aircraft.
Context Anchor
Seen in air traffic control radar, onboard weather radar, and discussions of how clearly radar can show aircraft or weather.
Derivation
Clutter comes from an older English word meaning a confused, noisy mess. On a radar screen, that's exactly what unwanted returns look like — a jumble of signals crowding out the ones that matter.
Why Pilots Care
Clutter can hide nearby traffic or weather returns, leading to missed conflicts or incorrect avoidance decisions if not recognized.
Analogy
It is like trying to see one important note on a desk covered with extra papers. The note may still be there, but the clutter makes it harder to pick out quickly.
Grounding Statement
Picture a radar screen where ground features and rain create a speckled background that hides the clean dots representing other aircraft.
Intuition Check
Do not read “clutter” as just a messy-looking screen. In radar use, it means unwanted reflected signals that appear on the display and can interfere with seeing the intended target.
Example Sentence 1
The controller advised that radar clutter from a line of thunderstorms was making traffic difficult to identify in that sector.
Example Sentence 2
The pilot reduced gain to clear terrain-induced clutter while scanning for traffic at low altitude.