Negative keyword
In pay per click advertising (PPC), negative keywords prevent your advertisements from displaying for particular keyword phrases. The process of adding in negative keywords to a paid search account is an important part of the optimization process, as it allows you to eliminate search queries which are unlikely to convert into a sale. For example, an individual may want to advertise for "hotel in Toronto," but does not want to display ads for the keyword "hotel jobs in Toronto." In this instance, the term "jobs" would be added as a negative keyword.
Negative keywords are often necessary for paid search campaigns that contain keywords on either broad match or phrase match. These match types will display your ad for additional search queries (i.e. search queries other than the actual keyword that was added to the account). Thus, removing irrelevant terms often becomes necessary.
An additional use for negative keywords is to funnel traffic to the most high converting and optimized campaign or ad group for a particular search query. For example, let's say that you advertise for both laptop and desktop computers and that you have ad copy that is specific to each. You may notice that some searchers who are searching for laptops are being showed desktop ads and vice versa. Negative keywords can be used to make sure that each searcher is showed the most relevant ad copy that is most likely to convert into a sale.[1]