| a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison. |
| an extraordinary or unusual thing, person, or event; an exceptional example or instance. |
once in a while
Occasionally, not very often, as in Once in a while I enjoy going fishing. [Mid-1800s] Also see every now and then; from time to time.