Acetals derived from
ketones by replacement of the oxo group by two hydrocarbyloxy groups $\ce{R2C(OR)2}$ ($\ce{R} \neq \ce{H}$). This term, once abandoned, has been reinstated as a subclass of
acetals.
Source: PAC, 1995,
67, 1307. (
Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1345 [
Terms] [
Paper]