if your stomach churns, you feel sick because you are nervous or frightened:
My stomach was churning on the day of the exam.
2 [intransitive and transitive] also churn up
if water, mud etc churns, or if something churns it, it moves about violently:
We watched the ocean churn.
if a machine, engine, wheel etc churns, it or its parts begin to move:
I pressed the gas pedal, and slowly the wheels began to churn.
to make milk by using a churn
churn something ↔ outphrasal verb
She's been churning out novels for twenty years.
churn somebody/something upphrasal verb
to damage the surface of the ground, especially by walking on it or driving a vehicle over it:
The lawn had been churned up by the tractor.
to move water, mud etc around violently
churn something ↔ up
The oars had churned up the mud, clouding the water.
3 British English
to make someone upset or angry:
Though she looked calm, in reality she was churned up inside.