Amidines of sulfinic acids, $\ce{RS(=O)OH}$; thus $\ce{RS(=NR)NR}$, e.g. $\ce{PhS(=NH)NH2}$ benzenesulfinamidine.
Source: PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1368 [Terms] [Paper]