Compound having a very high basicity.
Examples: Amide bases such as lithium diisopropylamide (LDA), potassium tert-butoxide + organolithium, some phosphazenes.
Source:
PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 512 (https://doi.org/10.1515/pac-2018-1010)