Definition - What does Trap mean?
A trap is a Web development technique applied to prevent users from exiting a Web page. A trap disables a user's ability to use the back button or other key to return to a previously visited Web page. Some websites use the tactic to prevent users from leaving the page in an effort to coerce them to visit other pages on the site.
Techopedia explains Trap
To exit a trap a user must either close the browser window or type a new URL into the browser bar.