A button in a posters profile that you press to ignore said poster. When a poster is on your ignore list and the ignored poster makes a post the post is present but the text is missing.
The ignore list is frowned on by most Sciforums members, and is generally regarded as the last bastion of a coward. It is akin to sticking your fingers in your ears and yelling "La la la la! I can't hear you! la la la la!" although it is acceptable in the case of muslim.