Dictionaries can be found in a kind of places online but if you do crossword puzzles you might want to specifically search for a crossword dictionary to aid you when you get into a challenging spot with a word.
A crossword dictionary often mixes a dictionary with a thesaurus to assist you narrow in on the word or phrase you are searching for. It is a definite must-have when you are doing a crossword puzzle, whether it be online or off.