From Longman Dictionary of Contemporary Englishseahorsesea‧horse /ˈsiːhɔːs $ -hɔːrs/ noun [countable] 
HBFa small sea fish with a head and neck that look like those of a horse
HBFa small sea fish with a head and neck that look like those of a horseExamples from the Corpus
seahorse• Inlaid into the front of the black-faced headstock is the familiar Gibson logo, and what looks like a stylised seahorse. 