unk-unk n. especially in engineering, something, such as a problem, that has not been and could not have been imagined or anticipated; an unknown unknown. Editorial Note: The Barnhart Dictionary of New English Since 1963 (Barnhart/Harper & Row...
paper airplane n. in aeronautics and aerospace, a flying machine that is strictly theoretical. Editorial Note: The adjectival form paper, referring to something that exists only in print or writing but not as a physical object, is fairly common...