To pronounce the sibilant letter s imperfectly; to give s and z the sound of th; -- a defect common among children.
- A speech defect or mannerism characterized by mispronunciation of the sounds (s) and (z) as (th) and (th).
- A sound of or like a lisp: "The carpenter['s] . . . plane whistles its wild ascending lisp” ( Walt Whitman).
- To speak with a lisp.
- To speak imperfectly, as a child does.
- To pronounce with a lisp.