pi character n (Printing, Lithography & Bookbinding) printing any special character, such as an accent or mathematical symbol, which is not normally obtained in a standard type fount Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014