Final answer:
A diffuser is a tool that causes airflow to be softer and provides textural definition to hair.
Step-by-step explanation:
The attachment that causes airflow to be softer and provides textural definition to hair is known as a diffuser. A diffuser is a tool that is used with a hair dryer to help distribute air more evenly and gently, reducing frizz and enhancing natural texture. It is often used on curly or wavy hair to promote curl definition without causing excessive heat damage.