• adjective:   characterized by antagonism or antipathy

  Example: "Slaves antagonistic to their masters"

• adjective:   indicating opposition or resistance
• adjective:   incapable of harmonious association
• adjective:   used especially of drugs or muscles that counteract or neutralize each other's effect
• adjective:   arousing animosity or hostility

  Example: "Europe was antagonistic to the Unites States"

• adjective:   opposing or neutralizing or mitigating an effect by contrary action

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