lisp vs speech disorder

lisp and speech disorder both are nouns.

Word	Noun	Adjective	Verb	Adverb
lisp	Yes	No	Yes	No
speech disorder	Yes	No	No	No

As nouns, speech disorder is a hypernym of lisp; that is, speech disorder is a word with a broader meaning than lisp:

lisp: a speech defect that involves pronouncing `s' like voiceless `th' and `z' like voiced `th'
speech disorder: a disorder of oral speech

Other hypernyms of lisp include defect of speech, speech defect.

lisp (noun)	speech disorder (noun)
a speech defect that involves pronouncing `s' like voiceless `th' and `z' like voiced `th'	a disorder of oral speech

lisp (verb)	speech disorder (verb)
speak with a lisp