A portmanteau of anachronism and acronym that describes an acronym or initialism that has been used so long and become so ingrained in common language that its original spelled-out meaning is unknown to many, if not most. As examples, consider ASCII (American Standard Code for Information Interchange), radar (radio detecting and ranging), SCSI (Small Computer System Interface), scuba (self-contained underwater breathing apparatus), and sonar (sound navigation and ranging). See also acronym, initialism, and portmanteau.