a. [f. as prec. + -AL.] 1. Geom., etc. Of, pertaining to, or of the form of a cycloid.
Cycloidal engine: an instrument used in engraving an ‘engine-turned design’ upon the plates for bank-notes, etc., as a precaution against counterfeiting; the graver-point having a motion compounded of translation and rotation. Cycloidal paddle: a name erroneously given to a paddle-wheel in which each float is divided longitudinally into several strips in a slightly retreating order, en echelon, so as to lessen the concussion and make the resistance more uniform (Knight). Cycloidal pendulum: a pendulum constructed to swing in a cycloid, so as to be perfectly isochronous.
1704. J. Harris, Lex. Techn., s.v. Cycloid, The space within this Curve and the Subtense … is called the Cycloidal Space.
1830. Kater & Lardner, Mech., xi. 159. Availing himself of this property of the curve, Huygens constructed his cycloidal pendulum.
1884. F. J. Britten, Watch & Clockm., 122. The upper part of the pendulum is a double cord hanging between two cycloidal cheeks to give a cycloidal path to the bob.
2. Zool. = CYCLOID a. a.
1872. H. A. Nicholson, Palæont., 326. The scales … are cycloidal in shape, and are arranged in an imbricate manner.
Hence Cycloidally adv., in the form of a cycloid.
1727. Chambers, Cycl., s.v. Phonicks, A smooth wall … arched cycloidally or elliptically.
