loll back
To flop, droop, or roll backward. Tom was so tired that his head kept lolling back in the car. After the meal, we all lolled back on the sofa to watch the football match.
loll back
[for a head] to fall or droop backwards. As he passed out, his head lolled back and struck the corner of the table. Her head lolled back and suddenly she was fast asleep.