What is /oos for?

Never really bothered with it, but now I tried HC and I see /oos command mentioned every now and then. What is it for?

It's a chat command that forces resync between client and server. It can be really helpful but should be used with moderation, especially when in a party, or people will teleport all over the place which can easily cause unnecessary deaths.

not to be confused with the ever popular: ?OOS

Chris did a post about desync a few months ago. It's a good read, especially if you're unfamiliar with what causes desync and/or what players can do to make it less common. I think the post is in the manifesto section it's been a few months so might have to dig a little.

Most people run a macro for /oos, I'm pretty sure. Pretty much all gaming mice support onboard macros but there are programs for them as well