Penis, small: A penis that is abnormally small, also known as micropenis. In medical practice, the dimension of the penis that is measured is the length. This measurement is taken along the upper surface of the shaft of the penis to the tip, using a measuring tape or preferably a ruler. The ruler is pressed firmly into the soft tissue over the pubic bone (the symphysis pubis) since, in obese boys and men, a seemingly small penis may be partly engulfed by the fat pad at its base and actually be quite normal in length. Normal standards are available for penile length. True micropenis reflects failure of normal development (a birth defect) of the penis or failure of normal hormonal stimulation of the penis.