From Longman Dictionary of Contemporary Englishstarfishstar‧fish /ˈstɑːˌfɪʃ $ ˈstɑːr-/ noun (plural starfish) [countable] 
HBAa flat sea animal that has five arms forming the shape of a star
HBAa flat sea animal that has five arms forming the shape of a starExamples from the Corpus
starfish• Many echinoderms such as starfishes and sea urchins also do this.• Unfortunately they feed exclusively upon live echinoderms attacking starfishes and sea urchins and can not be acclimatised to substitute foods.• Thousands of fertilized sea urchin eggs, starfish and blue clams returned to Earth with the astronauts.• Modern examples of those classes include starfish, spiders, worms, snails and eels.• Much of the current research on biological neural networks involves the study of invertebrate animals, such as sea slugs or starfish.• A word or warning also for anyone thinking of attempting to tear starfish apart to produce new animals.• Many attempts have been made simply to control the starfish.• The long slender arms are flexible, unlike the starfish shown previously. 