obtuse

Imagine explaining a clear point to someone who still does not get it, or does not seem to notice the hint everyone else can see. That person might be described as obtuse. In everyday English, it usually means someone is slow to understand or not sensitive to what should be obvious. Sometimes it also suggests they are being frustratingly unaware, and in some cases they may even be pretending not to understand. But obtuse is not only about people. In geometry, an obtuse angle is wider than a right angle: more than 90 degrees but less than 180. So, whether it is about a person or an angle, the word carries the idea of something that is not sharp.

The word obtuse has two main meanings, one used for people and behavior, and the other used in geometry. When you describe a person as obtuse, you usually mean they are slow to understand, slow to notice what should be clear, or insensitive to hints, feelings, or the point of a situation. It often has a negative tone because it can suggest a frustrating kind of slowness. Sometimes the person truly does not understand; sometimes they may be acting "deliberately obtuse" by pretending not to understand in order to avoid giving a direct response. Think of a character in a sitcom who keeps missing the point of a conversation or ignores an obvious hint.

In mathematics, obtuse has a very specific meaning. An obtuse angle measures more than 90 degrees but less than 180 degrees. It is wider and more blunt than an acute angle. This idea of bluntness can help you remember the everyday meaning too: the word often suggests a lack of sharpness, whether in understanding or in shape.

The word originates from the Latin obtusus, meaning "blunt" or "dull." This root perfectly connects both modern uses: a dull mind is like a blunt instrument, and an obtuse angle lacks a sharp point. Whether you are describing a person who misses a hint or measuring a shape on a page, obtuse signifies a lack of sharpness in either intellect or form. You might say, "His obtuse response only confused the issue further," or "The triangle was classified as obtuse because it contained one angle of 110 degrees and two acute angles."