(figuratively, idiomatic, informal, postpositive) Entirely, completely, extremely, to the greatest degree.
He was stuffed to the tonsils with cream crackers.
We had both been stuffed up to the tonsils with excellent food.
They sat there, robed up to the tonsils, and made me feel so below a juvenile delinquent.
With resentments choking him up to the tonsils.