Really good question! And welcome to the board, tbtran!...I'm just going through my "initiation" myself...you're in for a treat!

Wouldn't the opposite of acronym, then, be a word made up from the LAST letters of the words in a phrase? And since that doesn't happen often, does a word even exist for it? Perhaps you'll have to invent one...add to the language! I'll keep peeking in to see if someone comes up with an answer or solution.