contradict - (v.): if one thing contradicts another, the facts are so different that both statements cannot be true; to say something that is the opposite of what you said before; to say one thing, then do another

• Synonyms: challenge, oppose, go against, argue with, clash
  
• Antonyms: accept, agree, approve
• Origin:  L. contradicere from contra meaning "against"+ dicere meaning "to speak" (as in dictionary)
• Example: If you say you don’t like apples, but I see you eating them for lunch, then you have contradicted yourself!