ret·ro·vi·rus 
(rĕt′rō-vīrəs, rĕtrə-vī′-)
(rĕt′rō-vīrəs, rĕtrə-vī′-)n. pl. ret·ro·vi·rus·es
Any of a family of viruses, many of which produce tumors, that contain RNA and reverse transcriptase, including HIV.
ret′ro·viral adj.
retrovirusschematic of a retrovirus