an initialism

listen to the pronunciation of an initialism
الإنجليزية - الإنجليزية
abecedism

Brook is a verb, H.M. (as in HMS) is a well-known abecedism (how do you look in a pinafore? don't answer), and we all know what a peter is --.

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

BBC is an initialism for British Broadcasting Corporation.