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.
Heifer: A heifer is a female animal that has never had a calf. Once a heifer has a calf, she automatically becomes a cow. Bull: A mature male animal that is used for breeding. (And for the record, I did know what a bull was when I initially asked my city kid question!) Steer: A steer is a male animal that has been neutered.