slip 1 knitwise, knit 1 stitch, pass slipped stitch over
Skpo means, slip 1, knit 1, pass slip stitch over and is a form of left leaning decrease stitch.
To work this stitch, slip 1 stitch knitwise as if to knit it but just leaving it on your right needle. And then knit 1 stitch. You’re now going to want to pick up your slip stitch using your left needle and bring it over the top of your knit stitch and off the needle. It’ll look like this.