S0433400 (sī′fŭng′kəl)n. A tubelike structure in the body of a shelled cephalopod, such as a nautilus, extending through each chamber of the shell.[Latin sīphunculus, diminutive of sīphō, sīphōn-, siphon; see siphon.]si·phun′cu·lar(-kyə-lər), si·phun′cu·late(-lĭt) adj.EncyclopediaSeesiphuncle