A parking meter is a small machine that is mounted on a pole next to a parking space. When you want to park there, you need to pay for parking by putting coins into (feeding) the meter (more modern meters allow payment by cell phone or by credit card). How much time you get depends on how much money you put in.
There is no law against "feeding" someone else's meter, presumably so they don't get a parking ticket. However, the total time purchased is limited to whatever the maximum time allowed is. For example, if you park at a two-hour meter and put enough money in for two hours, you (or someone else) can't come back later and add more money to extend the time. Although in reality it's done all the time.
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