A cat with black or grey fur mixed with orange patches, creating a color pattern similar to a tortoise's shell. If it has white fur as well, it's a calico cat.
The vast majority of tortoiseshell and calico cats are female due to the genetic basis of cat coloration. Males are infertile due to an intersex condition, typically being XXY.
Some torties have a 'split-face' pattern. This is sometimes incorrectly attributed to genetic chimerism.
Examples
Split-face pattern
See also
Calico cat (also known as tortoiseshell-and-white)
