What is the definition or description of: tooth abnormalities?

Exactly: Exactly what your question asks. Any aberration in size, shape, position, color, health, function, support of a tooth is considered abnormal. To recognize "abnormal" dental students spend a year learning "normal." Once you know normal, variation from the norm becomes quite apparent. If you think you have an abnormal tooth or teeth, ask your Dentist to evaluate. We can't examine you.