Definition
The airspeed shown directly on the airspeed indicator, expressed in knots, without correction for instrument error, position error, air density, or compressibility. It is the raw reading the pilot sees on the cockpit airspeed gauge.
Plain English
The speed in knots that the airspeed gauge in the cockpit is showing right now, with no adjustments made to it.
Context Anchor
Seen in approach procedures, airplane manuals, and flight training discussions when a pilot is told what airspeed to fly.
Derivation
K stands for knots (one nautical mile per hour, a sea-based speed unit aviation inherited from marine navigation). IAS stands for Indicated Airspeed -- 'indicated' meaning what the instrument is showing, not a corrected or true value. Putting them together gives 'the knots reading shown on the airspeed indicator.'
Why Pilots Care
KIAS provides the reference speeds needed to stay within safe operating limits such as stall margins and approach targets.
Intuition Check
KIAS is not the airplane's speed over the ground. It is the speed shown on the airspeed indicator.
Example Sentence 1
The handbook calls for crossing the runway threshold at 70 KIAS with full flaps.
Example Sentence 2
The pilot noted the current KIAS and adjusted pitch to meet the target climb speed.