An obtuse triangle is any triangle that has an angle of more than 90 degrees. This differs from an acute triangle, in which all three angles are less than 90 degrees, and a right triangle, in which one angle is exactly 90 degrees.
Since the sum of the angles of a triangle is always 180 degrees, no triangle can have more than one obtuse angle. Any obtuse angle between 90 and 178 degrees is possible. A 178-degree angle would product an obtuse isosceles triangle with two acute angles of 1 degree each. The word "obtuse," also used to refer to a slow-witted or insensitive person, derives from the Latin word "obtusus," meaning dulled or blunt.