Well an explanation is what I am looking for.
I would call it a one-sided connection loss.
This "infinite lag" is when you cannot do anything, and the LAG icon is always showing. However, you can see new bricks being created and people chatting.
Once someone changes your position/velocity, you're able to control again, and any commands you sent during the "infinite lag" will all be sent at once.
This usually happens when you're uploading or have too many connections open.