nonselectively labelled

https://doi.org/10.1351/goldbook.N04202
An isotopically labelled compound is designated as nonselectively labelled when the position(s) and the number of the labelling nuclide(s) are both undefined.
Sources:
Blue Book, p. 517 (http://www.acdlabs.com/iupac/nomenclature/)
PAC, 1981, 53, 1887. 'Nomenclature of inorganic chemistry: II.1 - Isotopically modified compounds' on page 1896 (https://doi.org/10.1351/pac198153101887)