Reciprocity \Rec`i*proc"i*ty\, n. [Cf. F. r['e]ciprocit['e]. See {Reciprocal}.] 1. Mutual action and reaction. 2. Reciprocal advantages, obligations, or rights; reciprocation. {Reciprocity treaty}, or {Treaty of reciprocity}, a treaty concluded between two countries, conferring equal privileges as regards customs or charges on imports, or in other respects. Syn: Reciprocation; interchange; mutuality.