Spiritual Death is the separation of the soul (spirit) from God.
More Complete: Spiritual death is "a state of being in which the human soul is separated from God and has not been enlivened by his Spirit."
In the religious context, this is often considered to be of greater significance than the physical death.
One biblical passage used to explain spiritual death is Ephesians 4:18 as a state of being "alienated from the life of God."
Contrast Definition Physical Death is the separation of the soul (spirit) from the body.
Source: Keating C. 2002. Death: A Theological Position Statement. Available at: http://www.ntgreek.org/SeminaryPapers/systematic/Death.pdf