quaternary UK /kwəˈtɜː.nə.ɹi/US /ˈkwɑ.tɚˌnɛɹ.i/adjective 5noun 2forms 1 adjective5 •Of fourth rank or order. •having a quaternary ammonium group.The available anticholinergics are divided into the tertiary anticholinergics, which cross the blood–brain barrier, and the quaternary anticholinergics, which do not cross the blood–brain barrier. — 2013 •Composed of four elements. •Relating to or in number base four. •Of a mathematical expression containing e.g. x⁴. noun2 •The Quaternary period or the system of deposits laid down during it. •A quaternary compound. formsquaternaries
