He was the very 'definition' of a gentleman. [=he was a perfect gentleman]
The picture lacks 'definition'. [=the picture is not sharp/clear]
A glider is 'by definition' an aircraft with no engine.
(..) - What happened to Kane? - Something has attached itself to him. - We have to get him to the infirmary right away. - What kind of thing? - I need a clear definition. - An organism. Open the hatch. Wait a minute. If we let it in, the ship could be infected. You know the quarantine procedure... (..)1979 Alien