is likely misspelled.
has no English definition.
As a noun carbenium
is any carbocation.
carbenium
English
Noun
(en noun) (Often : carbenium ion)
(organic chemistry, informal) Any carbocation
Usage notes
* IUPAC recommends that carbonium is used instead.
References
* IUPAC
Not English
has no English definition. It may be misspelled.