She spent hours braining over the difficult math problem.

to think deeply or engage in complex mental activity.
He will brain this problem.
She brains the issue daily.
Let's brain this idea.
brain the issue
brain the problem
brain the idea
ponder
contemplate
ruminate
The brain controls all of our thoughts and actions.

The organ in the body that is responsible for thought, memory, and coordination of bodily functions.
My brain needs rest.
The brain is complex.
Use your brain wisely.
human brain
animal brain
computer brain
mind
intellect
cognition