Word Study
Siss
CIDE DICTIONARY
Siss, v. i. [Of imitative origin; cf. D. sissen, G. zischen.].
To make a hissing sound; as, a flatiron hot enough to siss when touched with a wet finger. [1913 Webster]
Siss, n.
A hissing noise. [1913 Webster]
For further exploring for "Siss" in Webster Dictionary Online