ruminate
US /ˈruː.mə.neɪt/
UK /ˈruː.mə.neɪt/

1.
think deeply about something
:
•
She spent hours ruminating on the meaning of life.
•
He needed time to ruminate on the offer before making a decision.
2.
(of a ruminant) chew the cud
:
•
Cows ruminate for hours each day.
•
The sheep were quietly ruminating in the field.