What does it mean to snub someone?

Usually:1: rebuke or to check or stop with a reply that hurts.

2: to check suddenly while running out especially by turning around a fixed object, much like a pole.

Snubbing is the way to pretend that a former friend is not so any more. It means "ignoring" even when you are close together. You are "turning your nose up" at them. Foolishly you might think that you are a better person than they are/ A most unwise assumption.