0 If someone who is thin fills out, they become heavier and more rounded, often because they have grown older.
When John is older and fills out some, he’ll be an outstanding athlete.
2 to write or type information in spaces that are provided for it:
His haggard face had filled out, his great freckles had faded away, and his red hair, through much pomade and skillful brushing, had grown darker and more manageable.
In time he filled out and became rather more shapely, but he was always an ungainly dog—"too big for his size," as Harry put it.
She is downright handsome,—or will be when she fills out a little.
