Lewis & Short

quantus-vīs, tăvis, tumvis, adj., as much as you will, as great as you please, however great, ever so great (class.): et manus una regit quantovis impete euntem (navem), Lucr. 4, 903; 4, 1171: quantasvis magnas copias sustineri posse, Caes. B. G. 5, 28: portum satis amplum quantaevis classi, for any fleet, be it ever so large, Liv. 26, 42: cum faciem videas, videtur esse quantivis pretii, Ter. And. 5, 2, 15: ingenium hominis, Gell. 4, 1, 2.
Neutr. subst.: quantum-vīs, however great an amount, as much as you will, how much soever, ever so much: meretrici des quantumvis, nusquam apparet, Plaut. Truc. 2, 7, 17: quantumvis tolle, Hor. Ep. 1, 7, 16.
With gen.: quantumvis fiduciae et spiritūs capias, how much soever, Nazar. Pan. Const. 19.
Adverb., very, very indeed: quantumvis facundus et promptus, Suet. Calig. 53.

    1. 2. For quamvis, although, albeit: ille catus, quantumvis rusticus, Hor. Ep. 2, 2, 39 (ap. Cic. Lael. 20, 73, and Sen. Ep. 85, 12, the true read. is quamvis).