Spirochaeta \Spi`ro*ch[ae]"ta\, Spirochaete \Spi`ro*ch[ae]"te\, n. [L. spira a coil + Gr. ??? hair.] (Biol.) A genus of Spirobacteria similar to Spirillum, but distinguished by its motility. One species, the {Spiroch[ae]te Obermeyeri}, is supposed to be the cause of relapsing fever.