Brim is the edge or rim of something, especially when it forms a projecting border. A hat's brim is the part that sticks out around the bottom to shade your face from the sun. A baseball cap has a brim in front, while a sun hat might have a wide brim that goes all the way around.

The word also describes when something is filled right up to the top edge. When you pour milk until your glass is filled to the brim, you've filled it so full that one more drop would spill over. A bucket brimming with water is about to overflow.

People use this second meaning figuratively too. Someone whose eyes are brimming with tears is about to cry. A student might arrive at school brimming with excitement about a field trip, so full of enthusiasm it's practically spilling out. When something brims over, like a pot of boiling water or a heart full of joy, it has reached its absolute limit and can't contain any more.