A fat persons hand upon making a fist. Because of the excess fat around the hands, knuckles are not defined. This means the fist is blob like and sometimes they have small dimples where pronounced knuckles can be found on the hand of a person of average build. This gives the appearence of a childs sculpting of a hand from child friendly Playdo modelling clay.
Having Playdo fists restricts the owners ability to deliver an effective punch if needed.
As Lucy sat writing her essay I noticed she had playdo fists