Turn the aerator housing counterclockwise and remove it from the faucet. Pull the O-ring off the tip of the faucet spout with your finger. The O-ring prevents leaking between the housing and the faucet. Set the O-ring in a safe place until you are ready to reinstall the housing.
After that, they are referred to as yearlings or stirks if between one and two years of age. A castrated male is called a steer in the United States; older steers are often called bullocks in other parts of the world but in North America this term refers to a young bull.
A bulla, bullae in plural, is the medical term for a large, thin-walled and fluid-filled blister. The walls of this type of blister are translucent, and the fluid inside can consist of lymph, blood, pus or serum, meaning any kind of clear bodily fluid.