This is the Isaac Mizrahi Live! Pebble Knit Cascade Bell Sleeve Dress (Style A305247) in black.

Fabric: The signature pebble knit blend (95% polyester, 5% spandex) that provides a stretchy, crepe-like texture.
Sleeves: Dramatic, double-layered cascading ruffle bell sleeves.
Hemline: A matching ruffle bottom hem that flares slightly at the base.
Fit: A scoop neckline with a semi-fitted silhouette through the bust and waist.