Real Dictionary

lisp
If someone has a lisp, they pronounce the sounds 's' and 'z' as if they were 'th'. For example, they say 'thing' instead of ' sing'.

LISP in American English
a high-level computer language used esp. in artificial intelligence
to pronounce or speak with a lisp
to substitute the sounds ( (θ) ) and (; ð) ) for the sounds of s and z, as in pronouncing sing as though it were thing
noun: a high-level programming language that processes data in the form of lists: widely used in artificial intelligence applications
noun: a speech defect consisting in pronouncing s and z like or nearly like the th- sounds of thin and this, respectively

lisp in British English
noun: a high-level computer-programming language suitable for work in artificial intelligence
noun: the articulation of s and z like or nearly like the th sounds in English thin and then respectively
verb: to use a lisp in the pronunciation of (speech)