Nonsense: something absurd, unreasonable, or meaningless. Also written as ノンセンス; used as a noun or quasi-adjective.
彼の言い訳はナンセンスだ。
His excuse is nonsense.
そんな噂はナンセンスだから気にしないでいい。
That rumor is nonsense, so you don't need to worry about it.
このジョークはちょっとナンセンスすぎて笑えなかった。
This joke was a bit too nonsensical to be funny.