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dull; uninteresting; boring; tedious
insignificant; unimportant; trifling; trivial; worthless
absurd; foolish; silly; stupid
useless; pointless; disappointing
この映画はつまらない。
This movie is boring.
つまらない話を長々と聞かされた。
I was made to listen to a boring story for a long time.
つまらなかったら途中で帰ろう。
If it's boring, let's leave halfway through.