What exactly is a ‘dotard’?

Kim Jong Un’s use of the arcane word “dotard” as a slam against President Donald Trump had many scrambling for a dictionary in search of its meaning and pronunciation.

What Exactly Is A 'dotard'?
What Exactly Is A 'dotard'?
What Exactly Is A 'dotard'?
What Exactly Is A 'dotard'?

What Exactly Is A 'dotard'?