to interrogate (a soldier, astronaut, diplomat, etc.) on return from a mission in order to assess the conduct and results of the mission.
to question formally and systematically in order to obtain useful intelligence or information: Political and economic experts routinely debrief important defectors about conditions in their home country.
to subject to prohibitions against revealing or discussing classified information, as upon separation from a position of military or political sensitivity.
Psychology. (after an experiment) to disclose to the subject the purpose of the experiment and any reasons for deception or manipulation.