General Opposites:
* Foreign: This emphasizes the origin being from another place or country.
* Introduced: This emphasizes the arrival being deliberate or accidental, rather than native.
* Non-native: This is a straightforward opposite, but it doesn't specify whether the origin is foreign or not.
* Exotic: This emphasizes the unusualness or foreignness of the origin.
More Specific Opposites:
* Alien: This emphasizes a lack of belonging or familiarity.
* Introduced species: This is specific to biology, referring to a species not native to a particular ecosystem.
* Non-endemic: This is another biology-specific term, referring to a species not naturally occurring in a particular region.
* Invasive: This implies that the non-native presence is harmful or disruptive.
The best opposite for "indigenous" will depend on the context of your sentence. For example, if you're talking about a plant species, "introduced species" might be the most fitting opposite. But if you're talking about a person's origin, "foreign" might be more appropriate.
Think about what aspect of "indigenous" you want to contrast and choose the word that best reflects that meaning.