A tabby, is any domestic cat with a distinctive 'M'-shaped marking on its forehead and one of 4 distinct coat patterns.
The patterns are the mackerel (striped), classic, ticked, and spotted tabby patterns.
A fifth pattern is formed by any of the four basic patterns being included as part of a patched pattern. A patched tabby is a cat with calico or tortoiseshell markings combined with patches of tabby coat, called caliby and torbie.