Noun
an angle between 90 and 180 degrees
Source: WordNetIt should be noted, however, that an edge with an acuter angle is more inclined to degrade quickly in combat situations than an edge with a more obtuse angle. Source: Internet
This problem was known (in a different guise) to Khayyam, Saccheri and Lambert and was the basis for their rejecting what was known as the "obtuse angle case". Source: Internet