Hijacking is used to describe several kinds of attacks where the attacker takes control of the session between a browser and a web server.
A browser hijack often shows up, for example, when someone’s home page, the page they see when they open their browser is not the one that they configured.
A web page hijack is where the attacker manages to redirect the traffic from search engines. When someone does a search and clicks on a search result of interest, instead of reaching the legitimate site, they will reach the attacker’s web page. There are a number of methods to do this and other consequences that may be severe. In one of the worst cases, the legitimate site may lose traffic until the search engine no longer proposes the site for relevant terms.
Account hijacking is another term used for attacks like phishing or spyware that succeed in collecting identifying and authentication information and allow the attacker to conduct business under the victims identity.
A man-in-the-middle attack is a special case of hijacking where the attacker controls both what’s seen on the browser and what’s seen by the web server.