Source : Webster's Revised Unabridged Dictionary (1913)

Spirillum \Spi*ril"lum\, n. [NL., dim. of L. spira a coil.]
   (Biol.)
   A genus of common motile micro["o]rganisms ({Spirobacteria})
   having the form of spiral-shaped filaments. One species is
   said to be the cause of relapsing fever.

Spirobacteria \Spi`ro*bac*te"ri*a\, n. pl.; sing.
   {Spirobacterium}. [NL. See 4th {Spire}, and {Bacterium}.]
   (Biol.)
   See the Note under {Microbacteria}.