lean back
1. To bend or recline backwards. Here, lean back on the sofa and put this ice pack on your head. She leaned back and whispered something in her friend's ear.
2. To bend or recline someone or something backwards. In this usage, a noun or pronoun is used between "lean" and "back." The barber leaned me back to wash my hair in the basin. I leaned the large bookshelf back so Tom could vacuum underneath it.
lean back (on someone or something)
to recline backwards, pressing on someone or something. Don't lean back on me! I'm not a chair! Lean back on the couch and tell me what you are thinking.
lean back
[for someone] to recline backwards, usually in a chair. Lean back and make yourself comfortable. Let's lean back and be comfortable.