- A plane curve, especially: (noun)
- A conic section whose plane is not parallel to the axis, base, or generatrix of the intersected cone. (noun)
- The locus of points for which the sum of the distances from each point to two fixed points is equal. (noun)
- Ellipsis. (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.