Definition of "directrix" []

• Mathematics A fixed curve traversed by a generatrix in generating a conic section or a cylinder. (noun)
• The median line in the trajectory of fire of an artillery piece. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "You probably feel at times like a chord of a conic section that passes through a focus and is parallel to the directrix, but know for certain that the phonemic differences between allormorphs of the same morpheme is supported by the idea that the quantitative measurement of many characters to the determination of taxa and to the construction of diagrams indicating systematic changes can make or break us."
• "Reminds me of a certain directrix of my acquaintance ... *sentence trails off as the speaker begins to stammer*"
• "The last story she would want circulating is one that makes her sound like Nazi film directrix Leni Riefenstahl brainstorming with Himmler and Goebbels over the specs for the Master Race's next generation."