What best describes an acute triangle?

An acute triangle is defined as a triangle where all three interior angles are less than 90 degrees. This characteristic ensures that each angle is acute, hence the name "acute triangle." In such triangles, the angles combine to meet the total angle measurement of 180 degrees, but none exceed 89 degrees, maintaining the acute classification.

The other choices describe different types of triangles. A triangle with one right angle refers to a right triangle, while a triangle with three obtuse angles cannot exist, as the sum of angles in any triangle must be 180 degrees and having three obtuse angles would exceed this total. Finally, a triangle that has at least one right angle describes a right triangle as well, which again doesn't apply to acute triangles. Therefore, the statement that an acute triangle has three acute angles is the correct and most fitting definition.