Consensus ad idem

A “meeting of minds”; also a splendid and unnecessary Latinism, for you might also describe this as an “agreement” sufficiently clear — if accompanied by at least a peppercorn of consideration — to be binding on the parties.

Just the sort of arrangement you might arrive at with your dry cleaner if, say, you had soiled your flannelette suit.

See also

• Latin
• Flannel