Biz Idiom of the Day- have a screw loose. have a screw loose Definition: To be a little bit crazy, or not acting normally. Example: 1) Paul has had a screw loose ever since his girlfriend left him. Etymology: A 'screw' keeps things together; when a screw is loose, things fall apart. So a person who has a screw loose is falling apart mentally. Synonyms: off the wall http://www.peakenglish.com/slang/dailybiz.jsp