na-adjective, noun
common person; foolish commoner; mediocrity
A somewhat literary or formal term for an ordinary, unenlightened person, often with a nuance of foolishness or lack of refinement. Can be used self-deprecatingly or to describe the masses.
凡愚の身では、その深遠な思想を理解できなかった。
As a mere commoner, I could not grasp that profound thought.
彼は自分を凡愚と称して、決して偉ぶらなかった。
He called himself a foolish commoner and never acted superior.