Webster’s Revised Unabridged Dictionary · 1913
Spirillum
Spi·ril′lum (spī·rĭl′lŭm), n. [NL., dim. of L. spira a coil.] (Biol.) A genus of common motile microörganisms (Spirobacteria) having the form of spiral-shaped filaments. One species is said to be the cause of relapsing fever.