From japanese "作画" (lit. "drawing"), it is used among western anime fans to refer to high quality animation in japanese animated series, movies, etc. When, at an important moment in the story of an anime, the quality of the animation improves drastically to make more impact or to be more dramatic or memorable, you can say that this moment is sakuga or has sakuga.
That fight scene is full of sakuga!
When character A hits character B in the face, it is pure sakuga.
This anime takes sakuga seriously.
When character A hits character B in the face, it is pure sakuga.
This anime takes sakuga seriously.