The most direct answer is that a Pilates body is a body that does Pilates consistently and enjoys at least some, if not all, of the many benefits of Pilates. After all, a large variety of people do Pilates, and they do it for a lot of different reasons. There are no rules about what a Pilates body has to look like or be able to do.
There are, however, certain ideals associated with the idea of a Pilates body, and there are tangible results to gain from practicing Pilates that bring one's body into close alignment with those ideals.
When Joseph Pilates developed this work, he did not talk about long, lean muscles, or flat abs as we see in Pilates body advertising these days. He was interested in the body as a total package of health and vitality, from which a pleasing external presentation—flat abs, better posture, balanced muscularity—is a natural result.
The Core of a Pilates Body
A true Pilates body starts deep inside with the body's systems of breath and circulation. Joseph Pilates emphasized the importance of this over-and-over in his writing. He said that, above all else, one should learn to breathe properly. Full breathing feeds and stimulates the circulatory system, which is a body cleansing process that detoxifies the blood and refreshes the cells. Here is the root of the vitality we need to enjoy life and exercise. When breathing and circulation are working well, the body also has a natural rhythm wherein the organs are toned and refreshed, and there is energy for daily life.
A body freed from nervous tension and over-fatigue is the ideal shelter provided by nature for housing a well-balanced mind that is always fully capable of successfully meeting all the complex problems of modern living. Joseph Pilates
In a Pilates body, a strong and flexible spine is of paramount importance. Pilates exercises are designed to make sure the spine is well-supported by the core muscles, and that there's proper alignment of all the bones. As Joseph Pilates said, the only real guide to your true age "is the degree natural and normal flexibility enjoyed by of your spine throughout life." As you investigate Pilates further, you will find the Pilates exercises are designed to strengthen, lengthen, and articulate the spine, which is part of why Pilates is famous for helping people with back pain.
A Pilates Body Moves with Grace and Efficiency
How a body moves, not just in the studio or gym, but in daily life, is the most important aspect of Pilates training; it wasn't developed just for looks. For Joseph Pilates, the point was to provide a method of training that would allow the body to do what is asked of it with grace, ease, and efficiency. Such a body has to be both strong and flexible, and it has certain qualities of movement, such as being centered and balanced, as well as flowing yet controlled. These qualities, or Pilates principles, are practiced consciously through Pilates exercises as the strength and flexibility that support them are developed.
Outside the Pilates Body - Uniform Development
What you see in an ideal Pilates body is uniform, function-appropriate, muscular development. In fact, strength without bulk is one of the aspects of Pilates that draws many people to it. Not only is uniform muscular development a pleasing visual, it is also a natural result of training the body to move at a high level of harmony and efficiency. Who can be truly flexible when their muscles are over-developed, or developed in an imbalanced way which leads to all kinds of weaknesses and compensations in the body?
And now for the coveted flat abdominal muscles Pilates promotes. They are nice. And, they are merely the natural result of a system of exercise that emphasis core strength and flexibility by way of the harmonious coordination of muscles and skeletal alignment in the service of graceful, efficient activity. The abs are strengthened, but they are also trained to work together properly (an often overlooked key to getting flat instead of poofed abs) in the context of an integrated body that is relating at a high level to itself and its environment.
Learn more, read: Get in Shape with Pilates
A Pilates Body is part of a "coordinated trinity of body, mind, and spirit" (Joseph Pilates).
We cannot leave a discussion of the Pilates body without acknowledging that the body is never seen as separate from the entire person. Unlike other types of "fitness" programs where the body is engaged and the mind left to wander or indulge in distraction, in Pilates we are always consciously integrating the body and mind, which in turn rejuvenates the spirit. Pilates is about helping a person enjoy her/his life experience at its highest potential. A Pilates body reflects that level of presence and vitality.