The phrase "squishy balls" usually refers to soft and flexible objects that can be easily squeezed or compressed with your hands, like stress balls or toys. Full definition
Start by lying on your side with a Pilates ring or squishy ball between the ankles and the arm outstretched with head relaxed (womenshealthandfitness.com.au)
These delightful little squishy balls of water absorbing polymer (they look like Jello marbles) offer endless ways to entertain, soothe, educate and stimulate little ones in fun sensory play. (mommyscene.com)
I really thought you were a giant, monstrous poop, not a 7 pound, 14 ounce squishy ball of cute.» (babygaga.com)