1) Speaking with defect 2) Talking in a way 3) Thpeaking like thith 
• (p. pr. & vb. n.) of Lisp
Mispronunciation of the sibilants s and z. ... Synonym: parasigmatism, sigmatism. ... (05 Mar 2000) ... 
(lisp´ing) a form of sigmatism in which th sounds are substituted for s and z.
Type: Term Pronunciation: lisp′ing Definitions: 1. Mispronunciation of the sibilants s and z. Synonyms: parasigmatism, sigmatism