TTC: What all those trying-to-conceive acronyms mean

There are a ton of acronyms that get thrown around in online fertility message boards. If you're new to the land of fertility, infertility and trying-to-conceive, here's where you can ask "what the heck does it all mean?"

Here's a primer:
TTC: What all those trying-to-conceive acronyms mean https://www.todaysparent.com/getting-pregnant/trying-to-conceive/ttc-what-all-those-trying-to-conceive-acronyms-mean/

What acronym had you perplexed? What one did you wish you had known before exploring online?