Defn: A curve traced by a point in the circumference of a circle which rolls on the convex side of a fixed circle.
Note: Any point rigidly connected with the rolling circle, but not in its circumference, traces a curve called an epitrochoid. The curve traced by a point in the circumference of the rolling circle when it rolls on the concave side of a fixed circle is called a hypocycloid; the curve traced by a point rigidly connected with the rolling circle in this case, but not its circumference, is called a hypotrochoid. All the curves mentioned above belong to the class class called roulettes or trochoids. See Trochoid.
EPICYCLOIDAL
Ep`i*cy*cloid"al, a.
Defn: Pertaining to the epicycloid, or having its properties. Epicycloidal wheel, a device for producing straight-line motion from circular motion, on the principle that a pin fastened in the periphery of a gear wheel will describe a straight line when the wheel rolls around inside a fixed internal gear of twice its diameter.
EPIDEICTIC
Ep`i*deic"tic, a. Etym: [Gr. Epidictic.]
Defn: Serving to show forth, explain, or exhibit; — applied by the Greeks to a kind of oratory, which, by full amplification, seeks to persuade.
EPIDEMIC; EPIDEMICAL
Ep`i*dem"ic, Ep`i*dem"ic*al, a. Etym: [L. epidemus, Gr. épidémique.
Cf. Demagogue.]
1. (Med.)
Defn: Common to, or affecting at the same time, a large number in a community; — applied to a disease which, spreading widely, attacks many persons at the same time; as, an epidemic disease; an epidemic catarrh, fever, etc. See Endemic.
2. Spreading widely, or generally prevailing; affecting great numbers, as an epidemic does; as, epidemic rage; an epidemic evil. It was the epidemical sin of the nation. Bp. Burnet.