Stepping outside
in
This is about asking or wanting to fight.
If someone says: Do you want to step outside? it usually means:
Let’s step outside because I want to beat you up.
Also:
Taking it outside.
Continuing it outside.
History:
If someone wants to have a fight with another person, and they want to be relatively civilized about it, then they invite the other person to go and have the fight outside. This could be outside the workplace, or a bar, or a friend’s house, etc. So, asking someone to step outside is usually considered to be an invitation to engage in a physical altercation.