frivolity

nouns

the trait of being frivolous; not serious or sensible
frivolity, frivolousness
is derived from
frivolous
antonym
seriousness
something of little value or significance
bagatelle, fluff, frippery, frivolity
acting like a clown or buffoon
buffoonery, clowning, frivolity, harlequinade, japery, prank
is derived from
frivolous