An acronym is an abbreviation consisting of initial letters that are read like an ordinary word.
English radar (pronounced [ˈreɪdɑɹ] ), from radio detection and ranging.
Acronyms contrast with alphabetisms, which are pronounced with the names of the letters (e.g. CD, HTML).
Sometimes acronym is used for abbreviations more generally, i.e. also for alphabetisms.
From Greek akro- 'tip' and -oonym- 'name'. The first attestation in the OED is from 1943.