sew ‧ er /ˈsjuːə,ˈsuːə $ ˈsuːər/ BrE AmE noun [countable]
[ Date: 1400-1500 ; Language: Old French ; Origin: esseweur , from essewer 'to carry away water' , from Vulgar Latin exaquare , from Latin ex 'out' + aqua 'water' ]
a pipe or passage under the ground that carries away waste material and used water from houses, factories etc