ichidan verb
put up a good front; keep up appearances; cover up
Used when someone tries to hide a mistake, flaw, or awkward situation by pretending everything is fine, often in a somewhat obvious or clumsy way. The verb combines 繕う (to mend, to patch up) with 立てる (to do something vigorously), emphasizing the effort to maintain a facade.
彼は失敗を繕い立てようとしたが、すぐにばれてしまった。
He tried to cover up his mistake, but it was soon found out.
彼女は笑顔で繕い立てたが、本当はとても悲しそうだった。
She put on a brave face with a smile, but she actually looked very sad.