STFD
STFD has 3 meanings
Slow the f*** down
CensoredSTFD is an aggressive way to demand that someone slows down, whether they are driving too fast, talking too fast, playing too fast, etc. People may use it in messages, online, or even to warn those speed demons driving too fast through a neighborhood.
For example, a gamer may message you "STFD!" if you are moving too fast through a level and they are following you. Or, if your friend starts sending you rapid-fire texts freaking out about her boyfriend breaking up with her, you might text back, "STFD. Take a deep breath and give me a call."
Example
Can you STFD?!? I'm trying to keep up!
Sorry, got carried away
Can you score under par in this golf terms quiz?
STFD is an aggressive and vulgar acronym people use to tell others to stop their actions. For example, if your annoying uncle insults others in a family group chat, you may message him, "STFD, Frank!"
You will most likely see STFD in arguments in texts and online in messages and forums. However, remember that STFD is intense and includes a vulgar word, similar to STFU, so you should reserve it for when you are serious.
While people typically use STFD metaphorically (often to express superiority over someone else), they may also use STFD when they really want someone to sit down. As you can imagine, this is pretty rare unless you teach an unruly class on Zoom.