From Kook Science
Strangeness is the quality or aspect of a thing (object, event, phenomena) that provokes a sense of alienation or disquiet in an observer, resultant the foreign or unfamiliar character of that quality or aspect. As a spectrum, low strangeness may be considered to be a thing arousing a small curiosity, but of such character that it does not cause anxiety that there is no clear explanation; while high strangeness falls on the opposite end, giving rise to the sense of being inexplicable, utterly alienating, and beyond reasonable explanation. For example: a bird falling from the sky, dead, is an event of low strangeness, insofar as it is unexpected and may arouse a sudden feeling of confusion or curiosity, but can be explained by any number of known causes; while a flock of birds, all featherless, glowing various throbs of green and blue, smashing into the ground to form luminous puddles, is an event of high strangeness, as it is not only unexpected, but also cannot be immediately explained under normal conditions. This spectrum, such as it is, cannot be taken as an objective standard, as there may certainly be those who would not find the latter example strange, and might consider it all perfectly normal and expected.