Passable means good enough to be acceptable, though not outstanding or impressive. When your teacher says your essay is passable, she means it meets the basic requirements but doesn't shine. If a trail through the woods is passable after a storm, you can get through it, though it might be muddy or cluttered with small branches.

The word often suggests something that barely crosses the line from unacceptable to acceptable. A passable imitation of your friend's voice might fool someone for a moment, but it's not convincing enough to trick anyone for long. A passable meal fills you up without being memorable or delicious.

Notice that calling something passable isn't usually a compliment. It's more like saying “this will do” or “I suppose this works.” Sometimes passable is genuinely all that's needed: a passable temporary fix for a broken shelf holds things up until you can make a proper repair.

The word can also mean able to be passed through or crossed, like when a road becomes passable again after snow has been cleared. In this sense, passable simply means navigable or traversable.