| 单词 | key course | 
| 释义 | > as lemmaskey course   key course  n. Building and Architecture (now rare) a course containing a keystone or consisting of keystones. ΚΠ 1700    Moxon's Mech. Exercises: Bricklayers-wks. 41  				The middle of the Key-course will be the middle of the Arch. 1835    Penny Cycl. III. 485/2  				A stone high up in the arch (for instance, a part of the key-course). 1977    C. M. Harris Hist. Archit. Sourcebk. 315/2  				Key course, a course of keystones in an arch; used in a deep archway where a single keystone will not suffice. < as lemmas  | 
	
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