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]
(..) ...the great king... ...to honor his word... ...should the end of all days be upon us! You... ...who lack all... ."hono? I have seen how you treat your friends. We came to you once, starving, homeless... ...seeking your help. (..)2013 The Hobbit: The Desolation of Smaug