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]
(..) Wait, what kinda weapon are we talkin' about here? The Thanos-killing kind. Don't you think that we should all have a weapon like that? No. You simply lack the strength to wield them. Your bodies would crumble as your minds collapsed into madness. Is it weird that I wanna do it (..)2018 Avengers: Infinity War