I.to swear together, Xen., Plut.
2.to promise by oath, τί τινι Soph.; ξυνώμοσαν θάνατον πατρί joined in swearing death against him, Aesch.
II.to join in a league or confederacy, id=Aesch., Thuc.
2.to form a confederacy with others, c. dat., Thuc.: in bad sense, to conspire, Hdt., Ar., etc.