When you put "slang dictionary" in the query it's going to significantly boost The Online Slang Dictionary's results, because you've included part of the site's name in the query.
If you just search squeege, Urban Dictionary is #2 and The Online Slang Dictionary is not in the top 10. If you just search "as much use as a chocolate teapot", Urban Dictionary is #5 and Online Slang Dictionary is #9.