The evil eye is a curse or legend believed to be cast by a malevolent glare, usually given to a person when they are unaware. Many cultures believe that receiving the evil eye will cause misfortune or injury.  Talismans created to protect against the evil eye are also frequently called "evil eyes".  
Everyone gets a dirty look now and then, and we usually think little of it (especially if we deserved it). For most of us it is soon shrugged off, but in many places belief in "the evil eye" is taken very seriously, and requires immediate action to avoid harm.