Hip relative?

Usage examples of stl.

The fans were stl too, although the weather had changed sharply overnight, the thick muggy air blown away and replaced by one of those clear blue-and-white days that were more spring than summer, so that, like Nadine, she wore a sweater buttoned over her blou ise.

There was no mention of current position--the family was recorded as being active in stl, slip, and rl-est.