In the work (already) cited or quoted. Used, typically in footnotes and endnotes, to cite in an abbreviated form a source that has been cited previously; frequently abbreviated as op. cit.

plural of smooth operator

A covert operation typically involving activities that are highly clandestine and outside of standard military protocol.

plural of black operation

Alternative spelling of uncooperative

plural of tour operator

(mathematics, functional analysis) An operator L such that for functions f and g and scalar λ, L (f + g) = L f + L g and L λf = λ L f.

plural of linear operator

plural of additive operation

plural of order of operations