Source : Webster's Revised Unabridged Dictionary (1913)

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.

Relapsing \Re*laps"ing\, a.
   Marked by a relapse; falling back; tending to return to a
   former worse state.

   {Relapsing fever} (Med.), an acute, epidemic, contagious
      fever, which prevails also endemically in Ireland, Russia,
      and some other regions. It is marked by one or two
      remissions of the fever, by articular and muscular pains,
      and by the presence, during the paroxism of spiral
      bacterium ({Spiroch[ae]te}) in the blood. It is not
      usually fatal. Called also {famine fever}, and {recurring
      fever}.

Source : WordNet®

spirochaete
     n : parasitic or free-living bacteria; many pathogenic to humans
         and other animals [syn: {spirochete}]