BDD is body dysmorphic disorder: a mental-health condition in which a person cannot stop seeing a “flaw” in how they look — a flaw other people barely notice, or do not see at all. The worry is not ordinary vanity or a bad-photo day. It can eat hours, spoil sleep, and push someone to hide, keep checking mirrors, or seek surgery that does not quiet the feeling. Doctors and serious writing use the name; it is not a casual insult. Though actually, people now stretch “dysmorphia” in everyday talk (“I have body dysmorphia today”) for ordinary insecurity. That looser use is common online, but it is thinner than the diagnosis. BDD is not the same thing as an eating disorder, even though the two can show up in the same person.