n. In anatomy and zoology: The union or connection of bones in the middle line of the body, either by confluence, by direct apposition, or by the intervention of cartilage or ligament; also, the part, or configuration of parts, resulting from such union or connection.n. Some point or line of union between two parts; a commissure; a chiasm: as, the symphysis of the optic nerves.n. Attachment of one part to another; a growing together; insertion or gomphosis with union: as, the symphysis of teeth with the jaw. See acrodont, pleurodont.n. Coalescence or growing together of parts so as to close a natural passage; atresia.n. In botany, a coalescence or growing together of similar parts.