For years, I put up with a leaky faucet ... you'll probably have a short faucet. In this case, the stem is very short, right underneath the handle. Once you've replaced the washer, you need ...

Now, check to make sure your faucet is not leaking. Leaks in an outdoor faucet can cause low water pressure, so you may want to repair this issue now to avoid dealing with it in the future.