Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014 ad·e·noids (ăd′n-oidz′) Tonsils at the back of the throat that are swollen due to infection. Adenoids can block breathi...