n An abbreviation formed by (usually initial) letters taken from a word or series of words, that is itself pronounced as a word, such as RAM, radar, or scuba; sometimes contrasted with initialism.
n A pronounceable word formed from the beginnings (letter or syllable) of other words and thus representing the phrase so formed, e.g. Benelux = the countries Belgium, Netherlands and Luxembourg considered as a political or economic whole.
n Any abbreviation so formed, regardless of pronunciation, such as TNT, IBM, or XML.