That quality of poetic diction which makes possible the felt change of consciousness experienced through poetry. Barfield uses it to denote a wide variety of effects (e.g. archaism), all of which produce in a reader a sense of the unexpected or unusual.

"[The] aesthetic value of strangeness" Barfield cautions, "overlaps, but does not coincide with, the ancient and proverbial truism that familiarity breeds contempt." It is not identical with "wonder" however:

for wonder is our reaction to things which we are conscious of not quite understanding, or at any rate of understanding less than we thought. The element of strangeness in beauty has the contrary effect. It arises from contact with a different kind of consciousness from our own, different, yet not so remote that we cannot partly share it, as indeed, in such a connection, the mere word "contact" implies. Strangeness, in fact arouses wonder when we do not understand; aesthetic imagination when we do. (PD 177)

See in particular "Strangeness" (PD 169-77).