Verb (1-dan, intransitive)
1.  to break (into pieces);  to be broken;  to be smashed
2.  to collapse;  to crumble;  to decline;  to cool (e.g. enthusiasm);  to dampen (e.g. one's will to fight)
3.  to become less formal;  to throw off reserve;  to become affable
4.  to become easy to understand (e.g. a story)
5.  to be worried