na-adjective, noun
very thin; flimsy; cheap; shallow
Describes physical thinness of objects, or figuratively shallow/cheap quality of ideas, arguments, or character. Often carries a negative, dismissive tone.
この紙は薄っぺらで、すぐ破れそうだ。
This paper is very thin and looks like it will tear easily.
彼の言い訳は薄っぺらで、誰も信じなかった。
His excuse was shallow and nobody believed it.