1. a slight, incomplete, or superficial knowledge (of something or someone): He had only a nodding acquaintance with Italian and didn't trust it to get him through the tour. Although we were neighbors for several years, we had only a nodding acquaintance.
2. a person with whom one is only slightly acquainted: I don't really know what he's like - he's only a nodding acquaintance.
[ 1860-65 ]