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The word "legendary" means to be very well known for something, famous. It also means to be based on legends and old, such as legendary kings, knights, creatures, etc.
Some synonyms for the word are: famous, mythical, traditional, imaginary, celebrated, distinguished, popular, heroic.
Use "legendary" in a sentence:
There was no other in the league as that one legendary player.
Here lies the tomb of the legendary King Edward II.