TB is an abbreviation for tuberculosis, a highly infectious, potentially fatal disease of humans and animals caused by the Gram-positive bacteria Mycobacterium tuberculosis. TB causes the formation of hard nodules (tubercules) and crusty dead spots in lung and bone tissue. People suffering from tuberculosis exhibit symptoms such as a bad cough and wasting debility.
Prior to the development of antibiotics such as penicillin, TB was known as "consumption" and was widely feared. Now, because TB infection is on the rise again as a common secondary infection accompanying AIDS, antibiotic-resistant strains have developed which could potentially cause major epidemics in the near future if alternate treatments aren't found.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.