Define: Broad Match
Broad Match: This method of Keyword Matching is the default match type for Google AdWords, Yahoo! Search Marketing, and MSN AdCenter. This keyword parameter typically provides the greatest volume of traffic however historically can deliver a lower relevancy with the click through. MSN AdCenter will sometimes insert a synonym if broad match is selected for a given keyword.
Example: With a search phrase such as "seo optimization" will display ads with queries such as "seo" and "optimization" in any order along with other terms (including plurals).