Spadix \Spa"dix\, n.; pl. L. {Spadices}, E. {Spadixes}. [L., a palm branch broken off, with its fruit, Gr. ?.] 1. (Bot.) A fleshy spike of flowers, usually inclosed in a leaf called a spathe. 2. (Zo["o]l.) A special organ of the nautilus, due to a modification of the posterior tentacles.