silliness

absurdity, asininity, balminess, brainlessness, craziness, daftness, dippiness, dottiness, fatuity, fatuousness, folly, foolishness, imbecility, inanity, insanity, lunacy, madness, nonsensicalness, nuttiness, preposterousness, senselessness, simplicity, wackiness, witlessness, zaniness

balderdash, baloney (also boloney), beans, bilge, blarney, blather, bosh, bull [slang], bunk, bunkum (or buncombe), claptrap, drivel, folderol (also falderal), folly, foolishness, fudge, hogwash, hokeypokey, hokum, hooey, humbug, humbuggery, jazz, malarkey (also malarky), moonshine, nonsense, piffle, poppycock, rot, rubbish, senselessness, stupidity, tommyrot, trash, trumpery, twaddle

facetiousness, flightiness, flippancy, frivolity, frivolousness, frothiness, levity, light-headedness, light-mindedness, lightness