Unintelligent means lacking the ability to think, learn, and solve problems effectively. When someone makes an unintelligent decision, they're choosing poorly because they haven't thought things through or don't understand the situation. An unintelligent comment might show that someone doesn't grasp what's being discussed.

The word often describes ideas or actions rather than people. A teacher might call a choice unintelligent (like copying homework instead of learning the material), or an engineer might call a design unintelligent (because it wastes materials or won't work properly). Calling a person unintelligent is harsh and usually unkind, since intelligence comes in many forms and people can be smart in different ways.

Something unintelligent lacks thought or good judgment. An unintelligent strategy in chess means making moves without considering what might happen next. An unintelligent response to a problem might make things worse instead of better.

The opposite would be intelligent, thoughtful, or clever. When you approach a problem intelligently, you think carefully and use what you know to find the best solution.