Definition
CONTAMINATED RUNWAY
A runway is considered contaminated whenever standing water, ice, snow, slush, frost in any form, heavy rubber, or other substances are present. A runway is contaminated with respect to rubber deposits or other friction‐degrading substances when the average friction value for any 500‐foot segment of the runway within the ALD fails below the recommended minimum friction level and the average friction value in the adjacent 500‐foot segments falls below the maintenance planning friction level.
Source: FAA Pilot/Controller Glossary (verbatim from the Federal Aviation Regulations).