o.n.o. (in advertisements in Britain, Australia, and New Zealand) abbreviation for (Commerce) or near(est) offer: £50 o.n.o.. Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014