vinyl carbenes 

https://doi.org/10.1351/goldbook.V06620
Carbenes having a vinylic group on a carbenic carbon atom R2C=CRC:R R2C+–CR=CR. E.g. H2C=CHC:H prop-2-en-1-ylidene.
Source:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1374 [Terms] [Paper]