Very thin or flimsy in a physical sense; or shallow and superficial when referring to content or character. Often written in kana (うすっぺら).
その本は内容が薄っぺらで、参考にならなかった。
That book was superficial and not useful as a reference.
薄っぺらな紙皿だとすぐに曲がってしまう。
A flimsy paper plate will bend easily.
彼の説明は薄っぺらで説得力に欠けていた。
His explanation was shallow and lacked persuasiveness.