A metaphorical block that someone
puts up after living with abuse or being bullied as a child or other such
circumstances. Doesn't happen
over night but "brick by brick" & leads to loss of friends & family.
"Pink Floyds The Wall" is about
a man named Pink who, after: losing his father in WWI, having an overprotective mother, abusive teachers, having his wife
cheat on him, and many
other things, builds a wall and shuts the world out.