Kepler kep·ler US/ˈkɛplɜr/ uncommon noun 1. German astronomer who first stated laws of planetary motion (1571-1630) SynonymsJohannes KeplerJohan Kepler Related words Word family Kepler's first lawKepler's lawKepler's law of planetary motionKepler's second lawKepler's third law Broader terms astronomer WordNet 2.1 (Princeton University). CMU Pronouncing Dictionary. WordNet 2.1 Copyright Princeton University. All rights reserved.