Video: No in Baby Sign Language. Signing: The sign for no is like that scolding teacher in high school that always says no to everything. The sign looks like a mouth saying no. Take your index finger together with your middle finger and tap them together with your thumb.Figure: No in Baby Sign Language.igning: The sign for no is like that scolding teacher in high school that always says no to everything. The sign looks like a mouth saying no. Take your index finger together with your middle finger and tap them together with your thumb. Figure: No in Baby Sign Language.