1 - Any person that is unwilling to listen to, learn from and heed the counsel and the wisdom of someone who has gone before them, and foresees the pain, consequences and heartache that lie ahead in the path the person has chosen.
2 - Someone who only learns by suffering and/or sad experience.
3 - A student of the School Of Hard Knocks.
Example #1 - A small child who has recently learned how to walk starts walking towards a table. The child can see under the table just fine because their line of sight is under the table, but their forehead isn't. The parent across the room starts waving their arms and yelling, "Look out!", "Stop!", "Watch your head!", "Wait!" Unfortunately, the child either doesn't listen, doesn't understand, or flat out ignores the parents warning, and walks right in the table. The child is knocked on their but, starts rapidly taking in air, let's out a shattering scream, and out of their forehead pops a knot (Also known as a goose egg). Thus the term knot head.
Example #2 - The young teenager, enamored and infatuated with another, that decides against the counsels of their parents, to engage in sexual activity, which eventually ends up in an STD, pregnancy, abortion or shotgun wedding and subsequent divorce.
Example #3 - The guy who buys a bullet bike and decides, against the counsel of his friends and family, to drive it fast and recklessly on the freeway, without a helmet or proper protective body gear, which ends up getting in a high speed accident and receiving serious disabling injuries.
(A) A person who has trouble thinking in a logical progression. this is usually caused by a profound amount of circular reasoning tying their brain into a knot.
(B) A dumb ass
That Knot Head Smerman is trying to figure out how to use the urinal again. last time he pissed his pants before he figured it out.