Akin to Smacktard slightly less offensive however. One can often call their friends a smackwad without being punched in the nuts on account of it not implying they are a retard... just a jerk. While -wad can be applied to a multitude of derogatory terms to imply the person is not just a 'jerk' for instance but a WAD of it (emphasis), smackwad is one of those words you can use is everyday conversation without really offending anybody enough to suffer repercussions.

A fool, a jerk

Someone who used to be a potential girlfriend/boyfriend, but no longer is.