Medical Definition of tar
1: any of various dark brown or black bituminous usually odorous viscous liquids obtained by destructive distillation of organic material (as wood, coal, or peat); especially : one used medicinally (as to treat skin diseases)—see coal tar, juniper tar, pine tar
2: a substance in some respects resembling tar; especially : a condensable residue present in smoke from burning tobacco that contains combustion by-products (as resins, acids, phenols, and essential oils)
Seen and Heard
What made you want to look up tar? Please tell us where you read or heard it (including the quote, if possible).