Grahaming is named after Martha Graham, who developed her own unique style of modern dance. Graham technique frequently uses contractions, which require lots of core strength and control.
Grahaming is like planking, but for dancers. Instead of assuming the plank position, one would assume a position typical of Graham technique and then take a photo as proof.
As with planking, the more unusual or challenging the location, the more fun Grahaming will be.
Bob: What the hell are those people doing?
Amy: They're Grahaming. Look, one of them just fell into the fountain! She must have not had much core strength.