An armpit fart is when you press your arm against your side and blow really hard through your bent arm. It makes a funny noise like a fart. The noise happens because the air that you push out has to go through your armpit. When it goes through your armpit, it makes the sound! It's just like when you blow on a blade of grass to make a noise. Armpit farts are really silly and a lot of people find them funny, so don't be afraid to try it out! Just remember to be kind to others and not make fun of them if they don't like armpit farts as much as you do.