The phrase "knock socks off" is used to describe the act of impressing someone greatly or stunning them with one's abilities or performance. While there are various synonyms for this phrase, antonyms are also useful in order to convey the opposite meaning. Antonyms for "knock socks off" include underwhelm, disappoint, bore, and fail to impress. When something underwhelms, it fails to meet expectations, and leaves one feeling unimpressed or dissatisfied. Disappointing someone involves failing to deliver on promises or expectations, which can generate a sense of letdown. If something is boring, it is uninteresting, dull, or unexciting, failing to engage or hold one's attention.