limaçon

from The Century Dictionary.

• noun Any univalve shell.
• noun A curve, invented and named by Pascal, generated from a circle by adding a constant length to all the radii vectores drawn from a point of its circumference as an origin, taking proper account of negative radii vectores.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Geom.) A curve of the fourth degree, invented by Pascal. Its polar equation is r = a cos θ + b.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun geometry A plane curve with polar equation or , of which the cardioid is a special case.