I still remember the time when I had to consult every unknown word with my print Collins dictionary. Frankly, I don’t miss it at all. It was just time-consuming. Nowadays, I look up novel words with WordWeb which is a dictionary and thesaurus in one package. It is joy to use.
WordWeb FREE offers 160,000 root words and 5000 audio pronunciations. WordWeb PRO offers 70 000 audio pronunciations and optional add-on dictionaries (e.g. Australian Oxford English Dictionary, Canadian Oxford English Dictionary). I use free version and I love it. The software works in offline mode, however, online mode offers more functionality e.g. access to Wikipedia. It can be used on Windows, Mac, iOS and Android.
Although some users complain that the interface looks outdated, in my opinion is simple and intuitive. However, audio pronunciation could be improved. Also, dictionary and thesaurus could be extended with a collocation dictionary. That would make a great dictionary perfect.