Entry 1 sense Webster, 1913 Caducous · Ca·du·cous · IPA /kəˈdjuːkəs/ 01 Dropping off or disappearing early, as the calyx of a poppy, or the gills of a tadpole. 1. Dropping off or disappearing early, as the calyx of a poppy, or the gills of a tadpole.(Bot. & Zool.)