I looked in the glossary but couldn’t find it. Sure hope someone knows.
I’m thinking it may be purl 2 together, slip slip stitch over the purl stitch but idk
If you just slipped two stitches, then pass the 2 slipped stitches over.
Context would be helpful. Can you link to the pattern? Maybe you could include the entire row instructions.
Here’s a video for p2sso that may help. It’s a centered double decrease and you may have it in several succesive rows to create a ridge as in the video or it may occur alone as part of a lace pattern.