abbreviation for

hepatitis-associated antigen; an antigen that occurs in the blood serum of some people, esp those with serum hepatitis
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Examples from the Web for haa

  • Mi faither says as haa snow is th' earth's lappin', and keeps all th' seeds warm, and mak's th' land so as it 'll groo.

    Lancashire Idylls (1898)|Marshall Mather
  • That is all she have done at present, but, ye see, she haan't been here so very long.

    The Woman-Hater|Charles Reade