Completely, totally, 100% — with nothing left out. It is an adverb, and it usually sits in front of an adjective or a past participle: wholly wrong, wholly responsible, wholly dependent on his parents. It is close in meaning to 'completely' and 'entirely', but it feels more formal and more written. You will meet it in news reports, in legal or business writing, in essays — not often in a friendly chat. If you say 'You're wholly right' to a friend, it sounds a bit like you are reading from a document. Two habits of the word are worth noticing. First, it very often appears in the negative, in the phrase 'not wholly': 'I'm not wholly convinced', 'The plan was not wholly successful.' Here it is doing something soft and polite — it does not mean 'not at all', it means 'yes, partly, but not all the way'. English speakers use it to disagree gently. Second, it fits naturally with words that already sound serious: wholly unacceptable, wholly inadequate, wholly owned. 'A wholly owned subsidiary' is a fixed business phrase for a company that another company owns every share of. Strictly, some careful writers say 'wholly' should describe a thing that has parts, so a whole thing can be spoken of — but in real use people simply treat it as a formal 'completely'.