Wiktionary
vb. 1 (context intransitive English) To lie down from a sitting position 2 To relax, to exert less effort
Usage examples of "lie back".
The fairie song came to his ears, compelling him to lie back down.
And whoso saith otherwise, I give him the lie back in his teeth, and will meet him face to face if I may.
The beginnings of the process in English must lie back in pre-invasion times, whatever may be true of its results, or of any of its vocalic effects sufficient to be recognized in spellings.
While she dressed across the room all he could do was lie back on the rumpled sheets and half doze.
She wanted to revel in it, to dance and sing, to simply lie back and let it roll through her, over her.
He would search for it rather aimlessly, but then give up, lie back in the armchair, and brood.
The movement clearly made him dizzy, but he did not lie back down.
The beginnings lie back in the Black Years, which only the lore-masters now remember.