What is "miasmic"

Usage examples of "miasmic".

Down in the cellars of the mansion, the miasmic, cloacal air was quite still.

I took it to be the spectral draco volens common in miasmic swamps like this one.

I think of it as the Engine for the Neutralizing of Information by the Generation of Miasmic Alphabets, but I appreciate that it does not exactly roll off the tongue.