Equinus

Jason rides his equinus into Vella's farm (TOS: "The Lost Warrior").

The equinus is a domesticated, single-toed, four-legged hoofed creature known to the Colonials, either akin or related to horses of Earth.

Equinus are "beasts of burden" working that appear with various coats in distinct colorations, spanning from near mono-tonality (white, brown, black) to multi-tonality. Multi-colored equinus feature distinct striping patterns, with one exhibiting an orange coat with black striping, much like the Earth tiger (TOS: "The Magnificent Warriors").

Apollo encounters numerous equinus after crash-landing on Equellus, the first being Puppis' Strider. Other equinus feature various colors and patterns of coats, including one such appearing much like the Earth tiger (TOS: "The Magnificent Warriors").

Starbuck encounters similar creatures in the form of unicorns on Attila, featuring a single protruding conical horn at the forehead (TOS: "The Young Lords").

Apollo, when exhibiting guilt over his disbelief regarding Chameleon's story about possibly being Starbuck's father, notes that he felt like an equinus' atrum (TOS: "The Man with Nine Lives").

Original Series definition: disparagement, akin to "horse's ass"; Apollo reveals feeling thusly for disbelieving Chameleon's suggestion that he might be Starbuck's father (TOS: "The Man with Nine Lives")