incommunicado
Concise Oxford English Dictionary © 2008 Oxford University Press:
incommunicado /ˌɪnkəmjuːnɪˈkɑːdəʊ/
▶adjective & adverb not able to communicate with other people.
– origin C19: from Sp. incomunicado, past part. of incomunicar ‘deprive of communication’.
'incommunicado' also found in these Oxford entries:

