Concatenation of slacker and bitch. A slackbitch is a person (generally female, but may be male) who is extremely lazy and prone to procrastination. The term is used as a playful, mocking insult, and is most often applied to oneself, not other people. Slackbitches are usually quite proud of being slackbitches.
I am such a slackbitch, I don't use hangers or drawers to hold my clothes, they just lie about on the floor in varying states of cleanliness.