Dictionary.net

• a law stating that the ratio of the square of the revolutionary period (in years) to the cube of the orbital axis (in astronomical units) is the same for all planets

2006 - WordNet 3.0
By Princeton University

• a law stating that the ratio of the square of the revolutionary period (in years) to the cube of the orbital axis (in astronomical units) is the same for all planets

2011 - English Dictionary Database
By DataStellar Co., Ltd