Your administration is not required to do anything about it--they have no obligation to prevent one employee from slandering another. (It would be good management to take action, but the law does not require good management). If slander has been committed, you would have the right to sue your colleague for monetary damages, assuming you can show monetary damages  (e.g. a loss of some opportunity or promotion)--if you can't show damages, there's really little or no point in suing.Bear in mind that defamation (slander is oral defamation) is only the following: the making of provably untrue statements of fact which damage a person's reputation. Profanity, insults, opinions, etc. are not defamation. So, claiming that you falsify time sheets, view internet pornography, or cheat on taxes or your spouse would be defamation (assuming that you don't do those things--if you do, they are true and not defamation).On the other hand, saying you're a "creep" is not defamation--that's just an opinion--as would saying you're "lazy" (another opinion). Saying that you're gay is not defamation, since it is not viewed as legally damaging to be called gay. Saying that you are not as qualified as coworkers is not defamation, if they do in fact have degrees, certifications, experience, etc. that you lack--in that case, it's the truth. Etc.