Sentence:  An angle less than a right angle is said to be "acute"; one greater than a right angle but less than a straight angle is said to be "obtuse"; one greater than a straight angle but less than a perigon is said to be <WSD>"reflex</WSD>" or "convex". 
Meaning of the word marked with <WSD> tags:  Having greater than 180 degrees but less than 360 degrees.