The phrasal verb "fill out" is frequently used in both informal and formal contexts, though it tends to appear more often in formal situations due to its association with paperwork and official forms. It is commonly employed when referring to the process of completing documents or forms by providing necessary information, such as filling out an application, a survey, or a registration form. In informal contexts, it might be used more casually, for instance, when telling someone to complete a form as part of a process or task they need to undertake. Additionally, "fill out" can also be used informally in a different sense, indicating a person gaining weight or developing a fuller body shape. This versatility in use underscores the importance of context for understanding the intended meaning of "fill out."
B1
PreIntermediate
1. To complete a form or document by entering necessary details.
Please fill out the application form and submit it by tomorrow.
He had to fill out several forms before he could get the loan.
2. To make something more detailed or complete by adding information.
She helped me fill out the proposal with more data.
Can you fill out this report with the latest numbers?
3. (Informal) To gain weight or become more muscular.
He's really filled out since he started working out.
The teenager began to fill out and looked more like a young man.