Can someone explain what this means:
Lamp posts and trees reared up at him, splintering his shins
Source: The Finkler Question by Howard Jacobson.
It means that lamp posts and trees injured the lower front part of his legs:
- To cause to split or break into sharp, slender pieces; form splinters.
- the front part of your leg between your knee and your foot: She has a nasty bruise on her shin.
The Free Dictionary
Lamp posts and trees do not literally 'rear up.' They are rather fixed.
But someone running, possibly in great fright, might experience coming upon lamp posts and trees in a way that they SEEMED to be jumping up to attack.
This is a poem, after all, and poetic imagery is appropriate. The emotional stress of encountering these obstacles is being communicated.