If you are miserable, you are very unhappy.

If you describe a place or situation as miserable, you mean that it makes you feel unhappy or depressed.

If you describe the weather as miserable, you mean that it makes you feel depressed, because it is raining or dull.

If you describe someone as miserable, you mean that you do not like them because they are bad-tempered or unfriendly.

You can describe a quantity or quality as miserable when you think that it is much smaller or worse than it ought to be.

A miserable failure is a very great one.