A term used frequently out of laziness, it means "can't be fucked" or "
couldn't be fucked" and in some cases "can be fucked" depending on the context.
For instance..
"I cbf
going to the movies"
would be "can't be fucked"
and..
"I cbf
getting up for work yesterday."
would be "couldn't be fucked"
where as..
"I'll go when I cbf"
would be "can be fucked"