Medical Definition of selective mutism
: an anxiety disorder of childhood characterized by consistent failure to speak in specific social settings (as at school) despite having the ability to speak normally in other settings (as at home) <If your child talks a lot at home but clams up at school—not uttering a word or even a laugh—she may have selective mutism, an extreme manifestation of anxiety.—Scholastic Parent and Child, February/March 2006>—called also elective mutism
Seen and Heard
What made you want to look up selective mutism? Please tell us where you read or heard it (including the quote, if possible).