May 29, 2020· An opening through which gases, especially air, can pass. the vent of a cask; the vent of a mould 2014, Elizabeth Kolbert, The Sixth Extinction: An Unnatural History, Picador, →ISBN, page 122: According to geologists who work in the area, the vents at Castello Aragonese have been spewing carbon dioxide for at least several hundred years, maybe longer ...