An SEO spam technique meant to railroad search engines into thinking that a web site is popular by artifically inflating apparent traffic to the site by repeatedly visiting one's own site with a search engine's search bar installed. Generally used by SEO-inept web marketers who are too lame to legitimately optimize their sites for search engines.
From the French, claque, meaning, "an organized group of supporters at a theatrical event who try to prompt positive audience response by clapping enthusiastically". Also a play on the traditional American English rendering of the sound made by a train traveling on a railroad, clickity-clack.
Some SEO spammers are such duh-weebs that after they get their sites banned from Google for keyword stuffing, doorway pages, and link farming, that they think they can still increase their PR, so they download Googlebar and play clickity claque.