adjective
sillier; -est
[also more ~; most ~]
having or showing a lack of thought, understanding, or good judgment :foolish or stupid
not practical or sensible
not serious, meaningful, or important
playful and funny
not used before a noun :in a condition in which you are unable to think clearly
adverb
informal :to an extreme degree
noun
[noncount] informal - used to address someone who is being silly