Definition: (in Canada) an indigenous American Indian community officially recognized as an administrative unit by the federal government or functioning as such without official status.
This is the common ASL sign around for a long time in ASL until the recent time that this sign is not considered acceptable by some Deaf indigenous individuals while other Deaf indigenous people choose to stay with this sign, based on discussions among Deaf American Natives / First Nations on the social media.
According to the discussions among Native Americans and First Nations over the past months on social media, this sign was proposed by a group of indigenous Deaf persons. There are some other Deaf indigenous persons who don't agreeably adopt it. Note that currently there is still an ongoing discussion.
If you are Deaf First Nations, you're welcome to submit videos, signing these words and/or your tribe, to this site.