Keyword is a Dimension in Google Analytics under the Traffic Sources section
Keyword Definition: For manual campaign tracking, it is the value of the utm_term campaign tracking parameter. For AdWords traffic, it contains the best matching targeting criteria. For the display network, where multiple targeting criteria could have caused the ad to show up, it returns the best matching targeting criteria as selected by Ads. This could be display_keyword, site placement, boomuserlist, user_interest, age, or gender. Otherwise its value is (not set).