As it happens, the ability to reproduce and the ability to respond to stimuli in any manner are generally accepted qualities that distinguish life from non-life.
Whether a given bunch of cells may be considered human is still very much an open question but whether a cell or cluster of cells is alive should be pretty easy to agree on.
http://www.biology-online.org/dictionary/Life http://dictionary.reference.com/browse/life
Whether a given bunch of cells may be considered human is still very much an open question but whether a cell or cluster of cells is alive should be pretty easy to agree on.