chew cud

chew one's cud

Fig. to think deeply; to be deeply involved in private thought. (Alludes to the cow's habit of bringing food back from the first stomach into the mouth to chew it, called chewing the cud.) He's chewing his cud about what to do next.
See also: chew, cud
References in periodicals archive ?
While humans may have longer intestines than animal carnivores, they are not as long as herbivores'; nor do we possess multiple stomachs like many herbivores, nor do we chew cud," the magazine adds.