Entry 1 sense Webster, 1913 Interstellar /ĭnˌ-tẽrs-tĕl'-ẽr/ · In·ter·stel·lar · IPA /ˌɪntərstˈɛlər/ 01 a. Between or among the stars; as, interstellar space. 1. Between or among the stars; as, interstellar space.