to try to make something seem less important than it really is
کم اهمیت جلوه دادن, کاستن از اهمیت, ناچیز جلوه دادن, ناچیز شمردن, کوچک شمردن, اندک انگاشتن
He always tried to minimize his own faults, while exaggerating those of others.
synonym play down