Dictionary.net

• the unit of measurement for the proportion of gold in an alloy; 18-karat gold is 75% gold; 24-karat gold is pure gold

2006 - WordNet 3.0
By Princeton University

• the unit of measurement for the proportion of gold in an alloy; 18-karat gold is 75% gold; 24-karat gold is pure gold

2011 - English Dictionary Database
By DataStellar Co., Ltd