mim·i·vi·rus 
(mĭmĭ-vī′rəs)
(mĭmĭ-vī′rəs)n. pl. mim·i·vi·rus·es
Any of a genus of double-stranded DNA viruses that are the largest of all known viruses.
[From mimicking microbe (since it is as large as the smallest known bacteria and was thought to be a bacterium when first discovered).]