It's explained in the films that the T-Virus is designed to reanimate dead tissue.
From the kentucky.com
Following the death of the Khat, the Ba and Ka were reunited to reanimate the Akh.
From the en.wikipedia.org
The team from Emerlan found him in cardiac arrest and tried to reanimate him.
From the thisismoney.co.uk
Human flesh cannot reanimate and then go after other humans as a food source.
From the kansas.com
In fact, selling a rotten fund might be just the thing to reanimate your portfolio.
From the usatoday.com
But Josephson's torpid background in physics struggled to reanimate itself.
From the guardian.co.uk
It just might reanimate your game with improved ball control and an enhanced sweet spot.
From the forbes.com
When a Hero dies, you can only bring it back by using the reanimate or resurrect spell.
From the en.wikipedia.org
When using the reanimate spell, the Hero will return to your Wizard's Seat as an Undead hero.
From the en.wikipedia.org
More examples
Animate: give new life or energy to; "A hot soup will revive me"; "This will renovate my spirits"; "This treatment repaired my health"
(reanimated) given fresh life or vigor or spirit; "stirred by revived hopes"
(Reanimated) Out of Jimmy's Head: Re-Animated is a live-action/animated television film that aired on Cartoon Network on December 8, 2006, the first original live action/animated production produced by the network.
Reanimation is the first remix album by American rock band Linkin Park as a follow-up to their first studio album, Hybrid Theory and released on July 30, 2002. Recorded during the Hybrid Theory tour in 2001, it features hip hop and electronica-influenced remixes of songs from Hybrid Theory.
To animate anew; to restore to animation or life; to infuse new life, vigor, spirit, or courage into; to revive; to reinvigorate; as, to reanimate a drowned person; to reanimate disheartened troops; to reanimate languid spirits; Being animate again
(reanimation) The act of reanimating; a second or subsequent animation
Any dead creature that is given the ability (by whatever means) to move and even think, though is not necessarily alive. Zombies are a good example.