So the keywords here are: bitterness-to-malt balance, palate-cleansing finish / not-lingering, sharpness.
In How to Judge Beer (Thomas Barnes, 2012) we have:
"Crisp: Slightly thinner-seeming body and little to no lingering sweetness or bitterness in aftertaste. Enhanced by higher levels of hop bitterness (but not astringency), cold temperatures, high carbonation levels and low levels of residual proteins, starches and unfermented sugars."
And
@mabrungard said in 2014:
"Three factors are strong influences on perceived crispness in a beer: pH, sulfate level, and fermentability. [...] High pH wort produces beers that are characterized as having 'dull' flavor. Reducing the mash and wort pH does improve 'crispness'. Including a modest level of sulfate in some beers can be an important factor in improving the dryness of the beer finish. Lack of sulfate can leave the finish a little too full or sweet."
--
Crispness, to me, is an impression of freshness and drinkability, provided by a set of sensations, like: dryness, absence of residual sweetness, reasonably high carbonation / light body / non-lingering finish.
But not necessarily all of them, since BJCP says, for example, that a Munich Helles is "soft and dry, not crisp and biting", and a Festbier is "well-attenuated and crisp, but not dry.
So, what do you think? Am I right?
Do you know any other source of definition for crispness?