'To spit upon' definitions:

Definition of 'To spit upon'

From: GCIDE

Spit \Spit\, v. i.
1. To throw out saliva from the mouth. [1913 Webster]
2. To rain or snow slightly, or with sprinkles. [1913 Webster]
It had been spitting with rain. --Dickens. [1913 Webster]
To spit on or To spit upon, to insult grossly; to treat with contempt. "Spitting upon all antiquity." --South. [1913 Webster]