Depending on the type of greeting:
* Farewell: This is the opposite of a greeting in terms of marking the beginning or end of an interaction.
* Ignoring: This completely avoids any form of acknowledgement.
* Insult: This is the opposite of a friendly or polite greeting.
Depending on the intent:
* Rejection: This implies a refusal of the greeting or the interaction it initiates.
* Dismissive: This suggests a lack of interest or respect in the greeting.
* Hostile: This indicates an unfriendly or aggressive response to the greeting.
Other possible antonyms:
* Departure: This refers to leaving, which is the opposite of arriving and greeting someone.
* Silence: This is the absence of any greeting.
Ultimately, the best antonym for "greeting" depends on the specific context and the type of greeting you're thinking of.