Plain English Meaning
It is the airspeed number you read straight off the airspeed gauge, in knots, with no corrections applied.
Full Definition
Indicated airspeed (IAS) is the speed shown directly on the airspeed indicator in the cockpit, derived from the difference between ram air pressure (from the pitot tube) and static air pressure (from the static port). KIAS is simply that value expressed in knots. It is uncorrected for instrument error, position error, air density, or compressibility effects.