| Word | Definitions | Synonyms |
|---|---|---|
| aplacental | (adjective) having no placenta | - |
| aplacophoran | (noun) deep-water wormlike mollusks lacking calcareous plates on the body but having fine slimy spicules on the covering mantle | Synonyms: solenogaster |
| aplanatic | (adjective) free from or corrected for spherical aberration | - |
| aplasia | (noun) failure of some tissue or organ to develop | - |