1. obsessional thinking involving excessive, repetitive thoughts or themes that interfere with other forms of mental activity.

It is a common feature of obsessive-compulsive disorder and generalized anxiety disorder.

2. the voluntary regurgitation in the absence of gastrointestinal distress (e.g., nausea, acid reflux) of food from the stomach to the mouth, where it is masticated and tasted a second time or ejected. It generally occurs during infancy (age 3–12 months); however, it may also be observed in individuals of any age, particularly those with severe intellectual disability. If it lasts for a period of at least 1 month following a period of normal feeding, it is diagnosed as rumination disorder; individuals may develop potentially fatal weight loss and malnutrition. Also called merycism. —ruminate vb.