surf [ surf ] noun Definition: foamy waves: the lines of foamy waves that break on a seashore or reef play in the surf verb (3rd person present singular surfs, present participle surfing, past and past participle surfed) Definition: 1. intransitive verb use surfboard: to ride waves on a surfboard 2. transitive verb ride waves in particular area: to go surfing in a particular place Have you surfed Waikiki? 3. transitive and intransitive verb online visit Internet sites: to go on the Internet for recreation, education, or entertainment, frequently changing the site [Late 17th century. Origin ?] surfable adjective surfer noun surfing noun. surfy adjective. surf's up US used to indicate that it is time to start doing something (slang) [source: Encarta]