To become steady, or to make something steady. It works both ways with no change of form: prices stabilized (they stopped going up and down by themselves), or the government stabilized prices (the government made that happen). What it really says is that a movement has stopped — the falling, shaking or swinging is over. Doctors use it constantly: "The patient has stabilized" means the danger of getting worse has passed, not that the patient is well. Money and news writing use it for prices, currencies, economies and countries. Engineers use it for physical things: to stabilize a ladder is to stop it wobbling; a camera with image stabilization holds the picture still while your hand shakes. There is also a slightly wider use for people and situations — after a hard year, someone's life stabilizes: it is not wonderful, but it has stopped falling apart. It feels formal or technical; friends chatting would say "things have settled down" or "it's calmed down". British spelling is often stabilise; American is stabilize. Both are fine — be consistent.