To pronounce the sibilant letters s and z imperfectly, as by giving the sound of th (as in thin) or Ŧh (as in this, either.)To speak imperfectly, as in childhood; make feeble, imperfect, or tentative efforts at speaking; hence, to speak in a hesitating, modest way.To pronounce with a lisp or imperfectly.n. The habit or act of lisping, as in uttering th for s, and Ŧh for z; an indistinct utterance, as of a child.