Here are some synonyms for contentious:
* Argumentative
* Controversial
* Disputable
* Quarrelsome
* Divisive
* Polemical
Here are some examples of how "contentious" is used:
* "The issue of gun control is a highly contentious one in the United States."
* "The meeting was contentious, with several attendees arguing loudly about the proposed changes."
* "Her views on social media are often contentious, but she never shies away from expressing them."
In essence, contentious describes something that is likely to provoke conflict or disagreement.