They called it a comet, 'for lack of' a better term/word. [=because they could not think of a better term/word for it]
His honesty, or 'lack thereof', is the real problem. [=the real problem is his lack of honesty]
There was 'no lack of' interest in the proposal. [=there was much interest in the proposal]
(..) and your power are needed. But always hold in your heart the pride of your special heritage. They can be a great people, Kal-El, they wish to be. They only lack the light to show the way. For this reason, above all, their capacity for good... ...I have sent them you... ...my only son. (..)1978 Superman