Salts of O-hydronated urea, having the structure [HOC(=NH2)NH2]+X− (and O- and N- hydrocarbyl derivatives).
Source: PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1374 [Terms] [Paper]