Meaning of initialism

(noun) a word formed from the initial letters of the several words in the name and pronounced as one word; "`NATO' is an initialism for North Atlantic Treaty Organization"; "the word `scuba' is an acronym for s(elf)-c(ontained) u(nderwater) b(reathing) a(pparatus)"

an abbreviation formed from the initial letters of the several words in the name and pronounced separately; "HTML is an initialism for HyperText Markup Language"