Digestive rumination

• In animals, rumination is a part of normal digestion, in which the animal (known as a ruminant
  Ruminant
  A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
  
  ) brings up swallowed food (usually grass or hay), chews it, and swallows it. This aids the animal by allowing it to eat quickly and chew later while it is resting.
• In humans, rumination syndrome is a generally involuntary eating disorder characterized by the regurgitation of recently ingested food without retching

Mental rumination

• Mental rumination
  Rumination (psychology)
  Rumination is a way of responding to distress that involves repetitively focusing on the symptoms of distress, and on its possible causes and consequences. Rumination is more common in people who are pessimistic, neurotic, and who have negative attributional styles. The tendency to ruminate is a...
  
   – contemplation or reflection, which may become persistent and recurrent worrying or brooding

Other

• Ruminations – a popular email column and series of books written by comedian Aaron Karo
  Aaron Karo
  Aaron Karo is an American stand-up comedian and author best known for his email column Ruminations, his web site Ruminations.com, his books Ruminations on College Life, Ruminations on Twentysomething Life, and I’m Having More Fun Than You, and his Comedy Central special The Rest Is History.In...