From Longman Dictionary of Contemporary Englishfantasticfan‧tas‧tic /fænˈtæstɪk/ ●●● S3 adjective 1 GOOD/EXCELLENTextremely good, attractive, enjoyable etc You look fantastic! It’s a fantastic place, really beautiful!► see thesaurus at good2 spokenGOOD/EXCELLENT used when someone has just told you something good SYN excellent, wonderful ‘I’ve passed my driving test.’ ‘Fantastic!’ That’s fantastic news!3 LOT/LARGE NUMBER OR AMOUNTa fantastic amount is extremely large SYN huge Kids spend fantastic amounts of money on CDs.4 IMPOSSIBLEa fantastic plan, suggestion etc is not likely to be possible fantastic schemes for making money5 [only before noun]STRANGE a fantastic story, creature, or place is imaginary and is very strange and magical SYN fantastical, → fantasy (3) fantastic tales of dragons and fairy queens —fantastically /-kli/ adverbTHESAURUSfantastic/terrific spoken extremely good, in a way that makes you feel excited and happy – used mainly in spoken EnglishThe view from the top was fantastic.He did a fantastic job.That’s a terrific idea!‘I passed!’ ‘That’s terrific!’great spoken extremely good – used mainly in spoken EnglishThanks for a great afternoon.‘Did you have a good holiday?' ’It was great!'excellent extremely good – used especially about the quality of something. Excellent is more formal than fantastic/terrific or great, and is used in both spoken and written EnglishOur local theatre has put on some excellent productions.It is an excellent film.wonderful extremely good in a way that impresses you or makes you very pleasedShe is really a wonderful person.That’s wonderful news!marvellous British English, marvelous American English extremely good in a way that impresses you or makes you very pleased. Marvellous sounds a little old-fashioned, but is still fairly commonWe had a marvellous dinner at a little restaurant near the hotel.Martino’s performance was marvelous. amazing extremely good in a surprising and exciting wayStanding there on top of Mount Fuji was an amazing experience.incredible extremely good in a surprising and exciting way. Incredible is often used when something is so good that it almost seems unlikelyWhat a goal! That was incredible!It was an incredible moment - one that I will never forget.brilliant British English informal extremely good‘How was your trip?’ ‘Absolutely brilliant!’What a brilliant idea!be out of this world used when saying that something is so good that you cannot imagine anything betterTheir desserts are out of this world.
Examples from the Corpusfantastic• My mom's sixty this year, but she still looks fantastic.• Teenagers spend fantastic amounts of money on clothes.• Airlines that rush to become launch customers get fantastic discounts from manufacturers.• It was horrible, but it gave me a fantastic feeling of self-confidence.• He's done a fantastic job.• They place at least one of their characters in a string of predicaments to which there are fantastic solutions.• fantastic stories of invisible men• Multicolored volcanic ash flows, long since hardened to jagged rock, reach into the sea like fantastic taffy mountains.Origin fantastic (1300-1400) French fantastique, from Greek phantastikos, from phantasia; → FANTASY