Related to stand-offish, a person or group is sit-offish when they choose to sit away from persons or groups they know because they are aloof or just assholes.
When the gang walked into they bar, they saw Brad and Janet sitting in a prime position. After their big falling out, the gang chose to be sit-offish and sit in a far corner of the bar.
When a couple is at a club, or in a public place, and are obviously avoiding each other, wether they know it or not.
Another example is, When boy friend & girl frienddon't talk to each other at school, or make other people believe they aren't even going out.
The economic historian Angus Maddison created the term "Western offshoots". According to Maddison’s classication, “Western Offshoots” consist of the United States, Canada, Australia and New Zealand.
David: "Hey that was nice, do you want to play monopolyright now"
Vivi: "Oh, not now, you know I have to drown the offshoots first. Plus, I would prefer to play scrabble."