Anisotropic
Imagine the two cars driving away from their home city - one car goes south on the highway, but the other takes the exit and drives towards the east to get around traffic. This illustrates how something that is not uniform in all directions (like a road network) can have different properties depending on where you look.
Technical definition
Opposed or unlike; in this context, referring to the velocity gradient model used in the study, which varies in magnitude and direction across different parts of the galaxy.