Like so many common verbs, the meaning of "know" in the Bible is varied and dependent on context. And in some cases -- when it is connected to ideas or objects -- its spiritual meaning and natural meaning are essentially the same. When the Bible talks about people knowing each other and especially when it talks about the Lord knowing people, the meaning has more to do with the states of love within people than it does with any factual knowledge. This makes sense if you think about it. When we really "know" somebody, what we mean is that we know what kind of person they are, what their motivations are, what they love, what they hate, what makes them tick. Those things are far more important than knowing their parents' names, where they were born or what year they graduated from school. Most often then, especially applied to people, "knowing" has to do with the perceptions we have about other people's loves and the conjunction that can exist between those with similar loves, not just a collection of facts.

In Ezekiel 26:11, this signifies the love of learning or intellectual things. (Arcana Coelestia 3727)

In Revelation 6:2, this signifies the love of understanding the Word. (Apocalypse Revealed 298)

In Zechariah 12:4, this signifies that the intellectual should be filled with falsities. (Arcana Coelestia 2383[2])

In general, 'a horse' signifies knowledge or understanding of the Word. In an opposite sense it signifies the understanding of the Word falsified by reasonings, and likewise destroyed from self-derived intelligence. 'A dead horse' signifies no understanding of truth from the Word.