In ice hockey, butterfly style is a technique of goaltending distinguished by the goaltender guarding the lower part of the net by dropping to the knees to block attempts to score. The butterfly style derives its name from the resemblance of the spread goal pads and hands to a butterfly's wings. The butterfly style is contrasted with stand-up style, where most shots on a goal are stopped with the goaltender on his feet.

https://en.wikipedia.org/wiki/Butterfly_style