noseeum UK /nəʊˈsiː.əm/US /noʊˈsi.əm/ noun2 •(informal) A biting midge, a small flying insect that harasses people outdoors, particularly in warm weather after sunset.Noseeums will go right through a tent screen. — 1983 •The inference that, because one cannot observe a reason for why something is true, that there is no reason why it is true. formsnoseeums