There are hundreds of on-line dictionaries and most of them are worth the bargain. Asking Google to define a word for you is the easiest thing to do when you are hunting for meanings. Otherwise you have a choice of dictionaries from where you can glean the meanings. But when you want to find synonyms and antonyms of a particular word, things can be hard on you if you are using any of them. I find most of the online dictionaries sufficiently incapable in that area. And I found Synonym.com can do that job easily for us.
Synonym.com comes with three features as you can see. It has a synonym finder that helps you find similar words. It has an antonym finder that helps you find the opposite words. It also has a definition tool so that you can also go find the meaning if you want.
One thing I liked about Synonym.com: They categorize the synonyms that they find for you and give you a list of words in different sense of the search word. This is one feature I haven't found in any of the Online Dictionaries. Most of them may give you a list of similar words. But they never tell you in what sense the given words are the synonyms of the search word.