nodding acquaintance
A casual or partial familiarity; a relationship which is not close or fully developed; an inexact understanding (of something).
None of the quarrymen were intimate friends of mine. I had a nodding acquaintance with them.
noun
The act by which one nods.
The Commons, on the other hand, upon permission being granted to appear at their Lordships' bar, come in with as many and as sapient noddings of the head, as a wooden mandarin performs in a tea-dealer's window[…]
adj
Having the flower facing downwards.