Self-ionizing solvent possessing both characteristics of Brønsted acids and bases, for example
H2O and
CH3OH, in contrast to aprotic solvent.
Sources:
Orange Book, 2nd ed., p. 30 (https://media.iupac.org/publications/analytical_compendium/)
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1083 (https://doi.org/10.1351/pac199466051077)