Definition
Aircraft systems designed to either remove ice that has already formed on critical surfaces (deice) or prevent ice from forming in the first place (anti-ice). Common examples include pneumatic boots that inflate to break off accumulated ice, electrically heated propellers and windshields, heated pitot tubes, weeping-wing systems that release a freezing-point depressant fluid, and engine inlet heat using bleed air or electrical elements.
Plain English
Equipment on the aircraft that either knocks ice off after it forms or stops ice from sticking in the first place.
Context Anchor
Seen in icing discussions, aircraft manuals, preflight checks, and instrument flying decisions when clouds, rain, or snow may be near freezing temperatures.
Derivation
De-' means to remove or reverse, so 'deice' means to take ice off. 'Anti-' means against or preventing, so 'anti-ice' means to keep ice from forming. The two prefixes capture the core difference between the two types of system: one reacts to ice, the other prevents it.
Why Pilots Care
Keeps wings, propellers, and engine inlets free of ice so the aircraft retains lift, power, and control.
Intuition Check
Do not assume deice and anti-ice mean the same thing. Deice removes ice that is already there; anti-ice helps keep ice from forming or sticking.
Example Sentence 1
Before departing into forecast icing, the pilot verified that the deice boots, heated propellers, and pitot heat were all functioning during the runup.
Example Sentence 2
The checklist requires verification that deice and anti-ice equipment is operational prior to flight in potential icing conditions.