AdWords keyword cleaning refers to the process of optimizing and refining a list of keywords used in Google AdWords campaigns. This involves removing irrelevant or underperforming keywords, adding new relevant keywords, and organizing the list to improve the overall effectiveness of the campaign. By regularly cleaning and updating the keyword list, advertisers can ensure that their ads are shown to the right audience, leading to higher click-through rates and conversions. AdWords keyword cleaning is an essential step in maximizing the success of online advertising efforts.