exfiltrate
Concise Oxford English Dictionary © 2008 Oxford University Press:
exfiltrate/ˈɛksfɪltreɪt/
▶verb withdraw (troops or spies) covertly from a dangerous situation.
– derivatives
exfiltration noun.
exfiltration noun.
– origin 1980s (earlier (C19) as exfiltration): perh. suggested by infiltration, infiltrate.
'exfiltrate' also found in these Oxford entries:

