Webster Dictionary meaning: a taunting, sneering remark. Those who use sarcasm are using their own pain, resentment and frustration to vent on others. They are looking for a reaction and they feed on the vulnerability of hurt feeling to feed their own ego. When they get a response or see the reaction is negative, it reinforces the attitude and this can become addictive behaviour. Do not react when you feel hurt unless you can address it in a positive affirming way that this attitude is not appropriate. This is their issue not yours.
Respond intelligently to unintelligent treatment – Lao Tzu in love and light