Definition of "cusp" []

• A point or pointed end. (noun)
• Anatomy A pointed or rounded projection on the chewing surface of a tooth. (noun)
• Anatomy A triangular fold or flap of a heart valve. (noun)
• Mathematics A point at which a curve crosses itself and at which the two tangents to the curve coincide. (noun)
• Architecture The point of intersection of two ornamental arcs or curves, such as the inner points of a trefoil. (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.

• "Not only are social mores (particularly regarding the role of women) depicted in striking detail, but the portrayal of a city on a technological cusp is given as well."
• "Again: if you think of the tracery in its _bars_, you call the cusp a redent; but if you think of it in the _openings_, you call the apertures of it foils."
• "The extremity of the cusp is a mere ball of Istrian marble; and consider how subtle the faculty of sight must be, since it recognizes at any distance, and is gratified by, the mystery of the termination of cusp obtained by the gradated light on the ball."