I’ve seen quite a few USC blog posts reminding students to always explain acronyms in the activities section. On my common app I listed LGBTQ Alliance (under LGBT activity type) and simply described it as a “school organization promoting acceptance and equality for queer students through education and outreach.” I didn’t have enough characters to list out the five word plus acronym, and I prefer to use queer as a general umbrella term for all identities. Probably over-worrying myself but this isn’t going to irritate an admissions counselor, is it?
No. The purpose is explaining acronyms is that there are many, many acronyms that the average person will have no idea what they are. I’d say that odds are 100% that every AO knows what LGBTQ means. 