Adjective describing a person who has no attention span or who is a poor listener. A person with the mental equivalent of tunnel vision. A dim bulb with a thick skull. A bone head.
My friend is so ha-block that I can't help but wonder what goes on in his head. I told him that I had two tickets to the movies for Friday night, and asked if he'd like to go. He replied by asking, "What are you doing Friday night? I was thinking of catching a movie."