Gawkiness is the way a person moves or behaves when their body does not feel easy to control. We most often say this about someone tall and thin, especially a young person who has grown fast and has not yet learned where their arms and legs end. They knock into tables; their hands seem too big; they look a little lost inside their own body. It is not the same as being careless. It is more that the body is still catching up with itself. People use the word with a small smile, often about teenagers, and many remember their own gawkiness as something that later went away. Though actually, said to someone's face it can still sting, because it points at the body. The word is not formal. You will hear it in stories and everyday talk more than in serious writing.