The original meaning of a smart ass in common terminalogy is a person who "thinks they know" how to do or what to do and tries to inject their opinion or effort "thinking they know better, when they really don't.
A dumbass is a person who "doesn't know" how to do or what to do and tries to either inject their opinion or effort not knowing what they are doing.
Don't believe me as someone who has true intellect that is older then 80yrs and they can tell you I am speaking what they learned. I was young and asked many people who all were my grandparents age, I am 39 currently and I am said to have an old soul however that is a phrase for wisdom beyond my years. Meaning I collected knowledge form people quite q bit older to have an understanding of the true definition of words we have since lost our foundation and it would be nice to get it back or retain what little we still have here in the USA
Jeff gets a prefab item that looks simple to put together, the instructions are in the box, he puts it together before reading the instructions and has left over pieces, he doen't know where they go.
(when all else fails read the instructions Smartass)
Phil gets the same prefab item and instuctions, he reads the instructions and doesn't understand what the instrucions are saying and still tries to put it together and has the same left over pieces.
(when all else fails and the instructions are beyond your grasp ask for help Dumbass)
Jerry gets the same prefab item and instructions and follows the directions, he has no left over pieces when it is completed. He comments on Phil as a Smartass and Jeff as a Dumbass and says your both stupid. Therefore he is a Wiseass and a Jackass for the uncalled for commentary, with the smartaleck remarks.