suru verb (irregular), intransitive verb
associate with; join the company of; stand alongside as an equal
Obsolete intransitive suru verb. Used in classical Japanese to mean keeping company with someone or being counted among equals. Not used in modern Japanese.
古語では「歯する」は同等の者として交わる意で用いられた。
In classical language, 歯する was used to mean associating as an equal.