The branch of science that studies death (especially its social and psychological aspects)

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"scientific study of death," 1837, from thanato- "death" + -logy . In 1970s, some undertakers made a bid to be called thanatologists ; but from 1974 that word has been used principally in reference to specialists in the needs of the terminally ill.

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Thanatology \Than`a*tol"o*gy\ (th[a^]n`[.a]*t[o^]l"[-o]*j[y^]), n. [Gr. qa`natos + -logy.] A description, or the doctrine, of death. --Dunglison.

Wikipedia Word definitions in Wikipedia
Thanatology is the scientific study of death . It investigates the mechanisms and forensic aspects of death, such as bodily changes that accompany death and the post-mortem period, as well as wider psychological and social aspects related to death. It is ...

Wiktionary Word definitions in Wiktionary
n. 1 The scientific study of the mechanisms and forensic aspects of death. 2 (context psychology English) The study of human aspects of death and the associated grief and rituals.

WordNet Word definitions in WordNet
n. the branch of science that studies death (especially its social and psychological aspects)