a geometric curve traced by a fixed point in one circle rotating around another fixed circle
epitrochoid in American English
(ˌepɪˈtroukɔid)
noun
Geometry
a plane curve generated by the motion of a fixed point on the radius or extension of the radius of a circle that rolls externally, without slipping, on a fixed circle. The epitrochoid is a generalization of the epicycloid
Word origin
[1835–45; epi- + trochoid]This word is first recorded in the period 1835–45. Other words that entered Englishat around the same time include: communism, faceplate, grandstand, placement, squeegeeepi- is a prefix occurring in loanwords from Greek, where it meant “upon,” “on,” “over,”“near,” “at,” “before,” “after” (epicedium; epidermis; epigene; epitome). On this model, epi- is used in the formation of new compound words (epicardium; epinephrine)