slow horse

comparing someones intelligence to the speed of a horse finishing a race. the slow horse would natrually finish last, therefore the person who is the 'slow horse' is not very bright. 1. someone of minimal intelligence or who does not understand simple concepts 2. someone who is illeterate 3. often used to call someone stupid when they dont understand something, commonly a simple joke 4. a dumbass can add the word "dusty" in front to mean a person who is both foul or dirty as well as unintelligent