Nodding Acquaintance Meaning

(idiomatic) Someone who is a remote or passing acquaintance.

Example: 1857, Wilkie Collins, The Queen of Hearts, ch. 5:
  None of the quarrymen were intimate friends of mine. I had a nodding acquaintance with them.
1910, Louis Joseph Vance, The Fortune Hunter, ch. 10:
  There isn't any doubt but that he had a nodding acquaintance with every pretty girl in town.
1940 April 22, "Education: Better than Shakespeare?," Time:
  [A] Northwestern University psychologist reported, for what it was worth, a surprising finding: an average college-educated modern man has at least a nodding acquaintance with four times as many words as Shakespeare used.
2004 July 12, Bob Herbert, "Opinion: The Real Enemy Staring Us in the Face," New York Times (retrieved 8 May 2013):
  A government with even a nodding acquaintance with competence and good sense would have launched an all-out war against Al Qaeda, not Iraq, in the immediate aftermath of Sept. 11.
1903, Arthur Quiller-Couch, The Adventures of Harry Revel, ch. 8:
  [T]o reach Cattewater I must either fetch a circuit through purlieus where every householder knew me and every urchin was a nodding acquaintance, or make a straight dash.
1922, John Galsworthy, The Forsyte Saga, part 3, ch. 5:
  He could not treat this scandalous matter in his own office. . . . Who was there he could go to? Linkman and Laver in Budge Row, perhaps—reliable, not too conspicuous, only nodding acquaintances.
2011 May 21, "Race-rigging scandal: We'll clear our names," Daily Mirror (UK) (retrieved 9 May 2013):
  [S]he knows only two of them as nodding acquaintances, and has never spoken to them privately.