Vari-bisexual is when one is both varisexual and bisexual. This can be due to experiencing shifts in sexual identity (.i.e biflexible) or feeling fluidity in their bisexual orientation (bifluid).
Vari-bisexual is a subset of variqueer specific to bisexuality. It can be seen as an umbrella term for identities like bifluid, fluid bisexual, abro-bisexual, etc.
It can also be a way of expressing one's identity as alternating, changing, and fluctuating without picking a label like bifluidflux or switching between sexual labels to describe oneself if one is bisexual and experiences one's sexuality fluidly.