Analogues of
alkenes in which a doubly bonded carbon atom is replaced by a heteroatom, e.g.
H2Si=CH2
methylidenesilane (silene less preferred),
MeN=CH2N-methylmethanimine.
Source:
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on
structure (IUPAC Recommendations 1995))
on page 1340