Of a dull brownish yellow, or drab color; -- applied to cloth, originally to a stout brownish cotton cloth, used in making uniforms in the Anglo-Indian army.
source: Webster 1913
a sturdy twilled cloth of a yellowish brown color used especially for military uniforms
source: WordNet 3.0
Any kind of khaki cloth; hence, a uniform of khaki or, rarely, a soldier clad in khaki. In the United States and British armies khaki or cloth of a very similar color is almost exclusively used for service in the field.