What is a brindle cat?
I believe that the proper terminology is “brindled cat” but people search for, “what is a brindle cat?”. A brindle cat is a tabby cat. Although the word “brindled” is used as a prefix to describe certain types of domestic cat coat such as the tortoiseshell. So for example, Sarah Hartwell, on her website messybeast.com writes about “brindled torties”.

A brindled cat – a tabby cat. This is a ‘toyger’ – a toy tiger and a rare cat breed. Photo copyright Helmi Flick.
Early alternative name for mackerel tabby
The “brindled cat” is an early alternative name for a tabby cat. Frances Simpson, the godmother of the cat fancy, and a great lady during the infancy of the cat fancy, writing in 1903, comments:
“[The tabby] was also called the brindled cat, or the tiger cat, and with some the grey cat – “graymalkin”. We are told also… that tabby cats in Norfolk and Suffolk were called cyprus cats, cyprus being a reddish-yellow colour, so that the term may be applied to orange as well as brown tabbies. The term “tiger cat” is, I believe, often used in America, and it well describes the true type of a brown tabby.”
‘Brindle’ used in describing coats of horse and dogs for example
I believe that you will find the word ‘brindled’ being used quite extensively to describe the coat of many other animals, mainly domestic animals such as horses and dogs. It describes a certain pattern much like the mackerel tabby (striped) pattern. I’ve included a photograph of a horse with a rare brindle coat on this page to provide an indication of what I’m referring to.

Photo published under creative commons license.
The word was then used to describe the mackerel tabby but as you can see it has fallen out of favor in describing the tabby but it is used by specialists and experts such as Sarah Hartwell in describing cat coat types in fine detail.
Wikipedia use the word in describing the tortoiseshell coat: “producing the characteristic brindled appearance consisting of an intimate mixture of orange and black cells…”
Dictionary definition
The dictionary definition’s reference to ‘streaks’ echos the tabby cat stripes:
“(especially of a domestic animal) brownish or tawny with streaks of other colour.”
Origin
It originally comes from an old Scandinavian word and was originally “brinded”. In a comment below this article you will see the words of the opening of Act Four, Scene One of William Shakespeare’s Macbeth which refers to “the brinded cat”. Apparently the word “brinded” in this context means “branded”. It is not actually a reference to the coat of a cat. The Elizabeth word for brindled is “streaked”.
P.S. Quora has it wrong. The authors describe the brindle cat as a tortoiseshell. I feel confident that my interpretation is correct as the terminology is based on cat history.