Entry 1 sense Webster, 1913 Microsporangium · Mi·cro·spo·ran·gi·um · IPA 01 n. A sporangium or conceptacle containing only very minute spores. Cf. Macrosporangium. 1. A sporangium or conceptacle containing only very minute spores. Cf. Macrosporangium.(Bot.) See: Macrosporangium