As dunb is not a word in English there is no simile for it.
dunb question
so dunb
you are so dunb \
Because he was dunb
itis because he is always looking at men and denining girls!
A simile.
A metaphor
As quick as a wink is a simile. ----
It is a simile.
simile It is an example of a simile (uses like or as). A simile in itself though is a type of metaphor.
simile
that man