Entry 2 senses · 2 variants Webster, 1913 Instar · In·star · IPA /ˈɪnstɑɹ/ v. t. n. 01 v. t. To stud as with stars. 1. To stud as with stars.[R.] 02 n. a postembryonic stage of life of an arthropod, especially an insect, between two successive molts; also, the arthropod when in that stage o… 1. a postembryonic stage of life of an arthropod, especially an insect, between two successive molts; also, the arthropod when in that stage of life.