Entry 1 sense Webster, 1913 Planetarium /plănˌ-ət-ĕr'-ē-əm/ · Plan·e·ta·ri·um · IPA /plænɪˈtɛəɹɪəm/ 01 n. An orrery. See Orrery. 1. An orrery. See Orrery. See: Orrery