Gruel is a thin, watery porridge made by boiling grain (usually oatmeal) in water or milk. Gruel has almost no flavor and barely any substance: imagine the saddest, thinnest bowl of oatmeal you can picture, then make it even thinner and blander.

For centuries, gruel was food for the very poor because it stretched a small amount of grain into many servings. In Charles Dickens' famous novel Oliver Twist, orphans in a workhouse survive on gruel so thin and unsatisfying that young Oliver dares to ask for more, leading to one of literature's most memorable scenes. Hospitals sometimes fed gruel to sick patients because it was easy to swallow and digest, though it provided little nutrition.

The word also describes any unappetizing, thin liquid food. If someone serves you soup so watery it's barely soup at all, you might call it gruel. Today, people rarely eat gruel except perhaps when recovering from illness, but the word survives as a way to describe something depressingly inadequate. When you read about characters eating gruel in historical novels, it's a signal that times are hard and food is scarce.