nod

Definitions

General English

  • noun a movement of the head up and down, meaning ‘yes’
  • verb to move the head slightly up and down, meaning ‘yes’
  • verb to move the head slightly up and down, to mean ‘hello’ or ‘goodbye’

Politics

  • verb to move the head forwards to show agreement

Military

  • acronym fornight-observation device
    (written as NOD)
http://www.dictionarycentral.com/definition/nod.html