This action is done by baseball pitchers to indicate that they are indeed on the mound.
It is done by inner city hoodlums as a sign of contempt, and as an indicator of their feeble intellect.
And it is done by cowboys as they gallantly open the door of a pickup truck for a lady.
As you walk past the open door of a public men's room, you can hear men hawking and spitting. As you walk past the open door of a public ladies' room, you cannot. Nobody has a good explanation of this phenomenon. Suffice it to say, spitting is a man's practice. Not even low life women spit much.
This includes saliva, water, chewing tobacco, etc.
3) To proverbiably make a grand show of disrespect towards values, rules, ideas, etc. Followed by 'on', 'upon', etc.
2) Randy drools while he sleeps, which explains the large puddle of spit on and around his desk.
3) After hearing me out, Randy spat upon my values and lied to his mother about the muddy hiking boots.