eu ‧ tha ‧ na ‧ si ‧ a /ˌjuːθəˈneɪziə $ -ˈneɪʒə/ BrE AmE noun [uncountable]
[ Date: 1600-1700 ; Language: Greek ; Origin: 'easy death' , from thanatos 'death' ]
the deliberate killing of a person who is very ill and going to die, in order to stop them suffering SYN mercy killing