Sentence:  [A] Northwestern University psychologist reported, for what it was worth, a surprising finding: an average college-educated modern man has at least a <WSD>nodding acquaintance</WSD> with four times as many words as Shakespeare used. 
Meaning of the word marked with <WSD> tags:  A casual or partial familiarity; a relationship which is not close or fully developed; an inexact understanding (of something).