- Lacking a siphon or respiration tube.
- Destitute of a siphon or breathing pipe; -- said of several bivalve shells.
- Any mollusk lacking a siphon or breathing tube.
- Not possessing a respiratory tube or siphon: opposed to siphonate; specifically, of or pertaining to the Asiphonata. H. A. Nicholson. In addition asiphoniate and esiphonate.