obtuse

adjective slow to learn or understand; lacking intellectual acuity so dense he never understands anything I say to him|never met anyone quite so dim|although dull at classical learning, at mathematics he was uncommonly quick|dumb officials make some really dumb decisions|he was either normally stupid or being deliberately obtuse|worked with the slow students
adjective lacking in insight or discernment too obtuse to grasp the implications of his behavior|a purblind oligarchy that flatly refused to see that history was condemning it to the dustbin
adjective of an angle; between 90 and 180 degrees
adjective (of a leaf shape) rounded at the apex