John Keats called it "negative capability".
From the reader's point of view -- in my intro to literature classes -- I call it "functional ambiguity".
I should define "it" in each case.
I am working on "that".
Postscript:
The key point is that just as the poet--according to John Keats--has to be "capable of being in uncertainties, Mysteries, doubts, without any irritable reaching after fact & reason" and so forth, the reader of literature, especially poetry, has to able to be capable of not-knowing-but-going-forward, capable of accepting that not everything in a poem, classic or contemporary, may make sense at first (or ever), capable of not stopping, not freezing, just because that reader doesn't understand fully the references, the phrasing, the character, or even the emotion. I call that concept "functional ambiguity," for what's unknown or ambiguous doesn't have to halt the reading.
Too many of my students get frustrated and stop attempting to understand when they feel swamped by what they don't yet know or understand. This is perfectly understandable, but often if we just keep reading a poem, for example, to the very end, the later material helps us to understand the earlier material -- or enough of a character, a situation, an emotion, or an attitude comes clear by the end that we can return to the beginning and get more from the second or third reading. And so forth.
By experience, accomplished readers tend to be "capable of being in uncertainties" and not getting swamped.
