Kawase blur effect
This is a faster version of the traditional "Blur" effect. It's recommended that you use this one rather than the "Gaussian" blur effect.
Use Blur to set the strength of the effect and Quality to trade a bit of performance for a smoother result.
The Pixelize X and Pixelize Y properties let you stretch the blur along one axis. Setting a higher value on a single axis gives a directional, streak-like blur (useful for a sense of speed or a vertical/horizontal smear).
Reference
All effects are listed in the effects reference page.