Webster's Revised Unabridged Dictionary · 1913

Siss

Siss , intransitive verb

[Of imitative origin; compare Dutch sissen, German zischen.]

To make a hissing sound; as, a flatiron hot enough to siss when touched with a wet finger. [Colloquial United States; Local, English]

Siss , noun

A hissing noise. [Colloquial United States]