Someone that lacks intelligence. Typically someone named Noah

When someone is a small brain they are not smart and have the smallest of brain's. People with small brain typically are named Roger and Bo.

Someone who always think of the negative side of everything

Someone who is dumb as fuck and has no culture. This person has almost always never gotten laid and eats apple seeds everyday.

When people have a small brain, they are not smart. In comparison, their brain is at least 2 times smaller, but in rare cases can be even smaller. Small brains usually: are brown haired, play volleyball, have a twin, named Madison.

"Small Brain" is an insult that implies that the person it's being attributed to has a small brain

when ur dumb