A spoonerism of "smart fucker", a humorous and frequently derogatory term used to describe someone who demonstrates intelligence (or a reasonable facsimile) in a conversation. Can be applied to males or females. First heard in the early 1990s. Identical to fart smeller
In conversation, it is sometimes followed by the correct pronunciation for humorous effect.
A person can be called a 'half-sucked fart' when they are just lazy, sloppy or bad at what they do.
It is especially effective when the person starts a job or activity which you know they have little or no skill at and they don't complete it.