a term used to describe the situation in which an individual is completely unresponsive to repeated electronic contacts (e.g., e-mails, telephone calls), as in, “I sent Janice two emails and a text yesterday but it’s just been radio silence from her”; derives from the military or maritime practice of stopping all radio communications for a set time, for instance to maintain operational secrecy; evokes the feeling of vague unease or dread that occurs in aviation when an airborne craft is incommunicado; this condition leads those who are attempting contact to speculate as to the cause of the subject’s inability or unwillingness to respond; in recent years this phenomenon is disappearing, as the prevalence of always-connected, omnipresent electronic devices makes it very difficult for anyone to be totally out of reach; can also refer to someone whose public communications (e.g., social media) have become dormant, usually for an unknown reason