To evaluate the expression \( \sqrt{19} - 32 \), we first consider each part:
- \( \sqrt{19} \) is an irrational number since 19 is not a perfect square.
- 32 is a rational number (it can be expressed as \( \frac{32}{1} \)).
When we subtract a rational number (32) from an irrational number (\( \sqrt{19} \)), the result will also be an irrational number.
Therefore, the answer is:
an irrational number.