iotacismus
/joʊˌtæsɪzəm/ or /joʊˌtætˈiːzəm/Definitions
1. noun
A speech impediment involving difficulty with the pronunciation of the ‘s’ and ‘z’ sounds, often resulting in their substitution with ‘t’ sounds, typically in the cases of /s/ and /z/ being pronounced as /t/ and /d/ respectively.
“The speech therapist helped the child overcome her iotacismus and improve her articulation of words like ‘bus’ and ‘buzz’.”