συνομνύναι
From LSJ
Τὸ γὰρ περισσὰ πράσσειν οὐκ ἔχει νοῦν οὐδένα → There is no sense in doing things beyond the usual measure
Greek > English (Woodhouse Verbs Reversed)
(see also: συνόμνυμι, συνομνύειν) conspire, agree to an oath, combine politically, form a confederacy, join in taking an oath, league together