The Collaborative International Dictionary
Peritrochium
Peritrochium \Per`i*tro"chi*um\, n. [NL., fr. Gr. ?; ? around + ? a wheel.] (Mech.) The wheel which, together with the axle, forms the axis in peritrochio, which see under Axis.
Wiktionary
peritrochium
n. The wheel which, together with the axle, forms the axis in peritrochio.