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.

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

plural of black operation

Alternative spelling of uncooperative

(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 additive operation

plural of order of operations

plural of operating loss

(mathematics) An extension of the differential operator, used in the theory of partial differential equations and quantum field theory.

The key word in a sentence.