Context #1:
David: So what are you going to do this weekend?
Sam: I had such a busy and stressful week at work, so this weekend I'm just going to kick back and get some rest.
David: That sounds good. Call me if you change your mind and you want to go out and do something.
Sam: All right.
Context #2:
Stephanie: When I was a kid, I lived way up in the mountains.
James: Really? Did you like living there?
Stephanie: Yeah it was pretty cool. After dinner, I used to go outside, kick back, and look at all the stars in the sky. It was so beautiful. In Los Angeles, we hardly ever see stars at night.
James: Yeah, that's true.
Meaning: to kick back means to relax and take it easy.
This idom comes from the LSI book titled Speaking Savvy. This book is used to teach Level 5 Speaking classes at LSI schools. For more information please visit idiomstudy.blogspot.com