'Terrifically' is an adverb meaning 'very' or 'extremely', used to make an adjective stronger: terrifically expensive, terrifically clever, terrifically funny. It carries a warm, slightly excited feeling — the speaker is impressed. It is close to 'incredibly' or 'tremendously' and a bit old-fashioned and British-sounding; it is more likely in writing, in reviews, or from an older speaker than in a young person's chat. A second use, less common, means 'in a way that is wonderful': 'the team played terrifically'. Here is the messy part worth knowing. The word comes from 'terror' and once meant 'in a frightening way'. English quietly turned that fear into strength — the same thing happened to 'terribly' (terribly sorry), 'awfully' (awfully kind) and 'dreadfully'. Today 'terrifically' has almost no fear left in it, though it usually keeps a positive or at least neutral colour, while 'terribly' leans a bit more negative. So 'terrifically hot' sounds like enjoyable excitement about heat; 'terribly hot' sounds like a complaint.

非常、極為、好得不得了。語氣偏正面、帶點讚嘆，跟中文的「超級」「棒極了」接近；不要理解成「可怕地」。