Compounds in which the oxygen of an aldehyde has been replaced by divalent sulfur,
RC(=S)H, e.g.
CH3CH2C(=S)H propanethial.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1372 (https://doi.org/10.1351/pac199567081307)