The equation \( y = -3 \) represents a horizontal line where the value of \( y \) is always -3, regardless of the value of \( x \). This means that for every \( x \)-value, there is one corresponding \( y \)-value.
Since each input \( x \) yields exactly one output \( y \), this equation does define a function.
Therefore, the answer is 1 (true).