| 释义 |
keystone
I. \ˈ ̷ ̷ˌ ̷ ̷\ noun
Etymology: key (I) + stone
1. : the wedge-shaped piece at the crown of an arch; especially : such a piece inserted last and locking the other pieces in place
2. : something analogous to the keystone of an arch in position or function : a part or force on which associated things depend for support
< the keystone of his faith >
< keystone of a system of defense >
as
a. : crushed stone of small size used in bituminous bound roads to fill the voids of the large aggregate — compare cover stone
b. : a bondstone in masonry
c. or keystone sack : second base in baseball
II. transitive verb
: to support by means of a keystone
III. noun
: a species of plant or animal that produces a major impact (as by predation) on its ecosystem and is considered essential to maintaining optimum ecosystem function or structure |