Effluvium \Ef*flu"vi*um\, n.; pl. {Effluvia}. [L., a flowing
out, fr. effluere to flow out. See {Effluent}, a.]
Subtile or invisible emanation; exhalation perceived by the
sense of smell; especially, noisome or noxious exhalation;
as, the effluvium from diseased or putrefying bodies, or from
ill drainage.
[1913 Webster]