If things are lying around, they are left in places where they should not be.

Has anyone seen my keys lying around? 有人看见我的钥匙落在什么地方了吗？

I wouldn't leave any money lying around the office if I were you. 我要是你就不会把钱在办公室里乱放。

to spend time lying down and doing very little

I spent a week in Spain, lying around on the beach. 我在西班牙呆了一周，在海滩上享受清闲。