Dictionary.com

Reputable dictionary brands with long history include: Collins, Oxford (specifically Learner's dictionary), Merriam-Webster, Longman. A very popular on-line dictionary is also https://www.dictionary.com/ , though I'm unaware whether it has any connections to the established classic dictionaries from the old days. All of these will feature multiple meanings, examples and various kinds of facts about each word. More on reddit.com

I collect used dictionaries at used book shops and garage sales whenever I can find them, and I'd love to get some modern dictionaries to update the collection, but I'm afraid I'm just too much of a cheap bastard to make the investment for a Merriam-Webster's or American Heritage. For up-to-date definitions, I use the Merriam-Webster App, which is free to use and allows me to save a list of favorite words. I also have a great love for Samuel Johnson's Dictionary of the English Language, published 1755, of which I own a facsimile copy. Not for current definitions, mind you, but because his definitions are simply eloquence made manifest, and his illustrative quotations are sublimely selected. More on reddit.com

There is no single best or most complete or most authoritative dictionary or dictionary website, and it's best if you don't rely on just one, because dictionaries have different purposes or philosophies and will differ in how they present senses or nuances. Also, general purpose dictionaries are aimed at native speakers, and may provide definitions that seem circular or overly complex to a learner. To that point, I recommend using OneLook , which links you directly to entries from several different dictionary websites. For learners, I recommend Oxford OALD , Macmillan , Cambridge CALD , Longman , or Merriam-Webster MWLD (especially for American usage). Collins COBUILD is also popular, but I personally don't like the way they present the material. The Cambridge Dictionary and Collins Dictionary websites can be useful because they search multiple dictionaries at once, although in my experience (including on this sub), this has served to confuse learners as much as it helps them. For general purpose dictionaries, Lexico (formerly Oxford Living Dictionaries) and Cambridge are reliable for British uses and Merriam-Webster and the American Heritage Dictionary for American uses. AHD is more linguistically conservative than MW. If you are dealing with historical texts and want something truly comprehensive, the most authoritative resource is the Oxford English Dictionary (not just any English dictionary published by Oxford, but the work known as the OED). This is a historical dictionary that attempts to catalog all meanings that all words have ever had since the dawn of the English language itself, including senses that may not have been used in hundreds of years. It is structured very, very differently from general purpose dictionaries and not intended for everyday use, but it is fascinating to read through some of the entries. More on reddit.com

I really like https://wordreference.com More on reddit.com