| a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison. |
| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
never
In addition to the idioms beginning with never, also see better late than never; it never rains but it pours; lightning never strikes twice; now or never; watched pot never boils; wonders will never cease; you never can tell.