What does the figure of speech his stomach rolls over then settles into a dull churning means?

The figure of speech "his stomach rolls over then settles into a dull churning" conveys a sense of anxiety or unease. The imagery of the stomach rolling over suggests an initial jolt of discomfort or fear, often associated with nervousness. The subsequent "dull churning" indicates a lingering feeling of tension or worry that persists, highlighting the emotional turmoil the person is experiencing. Overall, it vividly illustrates a visceral reaction to stress or apprehension.