Being approached by a person who you don't particularly want to talk to (i.e. a random), but who you nevertheless must talk to in order to avoid social awkwardness.
I got rambushed by that vaguely retarded guy while my boss, who is his father, was watching and I had to make conversation with him.
A circular rumbus is a brand new shape created by @rayaofsunshiine on twitter. It is a very amazing brand new shape and everybody should use it in the future. It is a true masterpiece. This is what it looks like from @rayaofsunshiine themselves: