Polyfluid is a combination of polygender and genderfluid, meaning someone is fluid between combinations of genders, or sometimes has multiple genders at once, sometimes not.
For example, someone can have the identities of male, female and neutrois, and be fluid
Another example would be someone fluctuating between the amount of gender identities they have.
This term was coined by user u/GlazeTheArtist on subreddit r/lgballt, who wanted a more specific term for their gender identity.
The flag is similar to the polygender flag, but is arranged more like the genderfluid flag.