Fill out often means 'complete a form or document', usually one where spaces have been provided for you write in. If you want to join the gym, please fill out this form. A person can also fill out.
Listen to 'English on Repeat,' a podcast to help us improve our speaking skills: Is this the right form?| Can you help me fill in this form?| What does this mean? | Do I have to fill in every part?
Listen to 'English on Repeat', a podcast to help us improve our speaking skills: Is this the right form?| Can you help me fill in this form?| What does this mean? | Do I have to fill in every part?