initialism

noun

1. A term formed from the initial letters of several words or parts of words, which is itself pronounced letter by letter.

   “The term BBC is an initialism for the British Broadcasting Corporation.”

2. The process of forming words or terms using initial letters of other words.

   “The next most frequent source language was English, with neologistic compounds accounting for 15 etymologies, with 9 other English-based terms from a variety of word formation processes such as initialism and semantic extension.”