intransitive verb
Definition: To speak in a way that makes the sounds of 's' and 'z' come out like 'th', often due to a speech difficulty.
Example: The child began to lisp when he was learning to talk.
noun
Definition: A speech difficulty where someone pronounces the sounds 's' and 'z' incorrectly, often saying them like 'th'.
Example: The child worked with a speech therapist to correct his lisp.
transitive verb
Definition: To speak in a way that makes it sound like the speaker has difficulty pronouncing certain sounds, especially 's' and 'z', often producing a 'th' sound instead.
Example: He tends to lisp when he is nervous.