Sleeping in is one of the best things to do on a lazy day. It is a great way to recharge your body and mind. If you want to mix things up a bit, you can use some new words to describe sleeping in. For instance, you can use the word "slumbering" to sound more poetic or sophisticated. You can also say "snoozing" or "dozing off" to imply that you are resting but not necessarily in a deep state of sleep. If you want a more casual term, you can use "lie-in," which is commonly used in the UK. Overall, there are many words you can use to describe the joy of sleeping in.