Cutie patootie is a made up term of endearment that means something is absolutely adorable. It rhymes and sounds like baby talk.

Louis and Jagadeesh are both right, but Jagadeesh has the usage right. It could be a term of affection. I'd never use the phrase to describe an adult, unless I was teasing, or joking. I could call my husband "my cutie patootie." I could also use it to describe a small child. "she's such a cutie patootie!"

Haha! It's just a made up expression based on the sounds the words make and that they rhyme. It's commonly called "baby talk" here in the US. Cutie means "very cute". Cutie patootie means "so cute I could just die" (there are a lot of idioms in baby talk - like "he's so cute I could just eat him up!".

It means "nice butt" (nice buttocks). I hope this helps. :)