The adverb form of toe-curling: to an embarrassing degree. You put it in front of an adjective to make the embarrassment stronger and more vivid — toe-curlingly bad, toe-curlingly awful, toe-curlingly awkward, toe-curlingly embarrassing. Almost every time you meet it, the adjective after it will be a negative one, because the word exists to push 'bad' further into 'so bad I cannot watch'. Reviewers of films, plays, and books love it. It is informal, a bit playful, and shows up far more in writing about performances than in ordinary conversation, partly because it is a mouthful to say. Because it is a long word doing an intensifying job, one is plenty — you would not use it twice in the same paragraph. Like the adjective, it can occasionally describe intense physical pleasure, but that use is rare enough that you can meet it and move on.

尷尬到不行地、令人尷尬到極點地（用來加強後面的形容詞，例如 toe-curlingly bad ＝ 爛到讓人尷尬癌發作）。台灣口語會說「有夠…」「…到爆」「…到不行」，位置和作用一樣。