Bareback

adv. without a saddle

Bareback can refer to A rodeo event, riding bucking horses without a saddle, see Bronc ridingriding horses without a saddle, see Bareback ridingbareback, a sexual slang term which refers to sexual intercourse, usually homosexual, without the use of a condom"Bareback" is the title of a B-Side of "Growing on Me" by The Darkness, commonly the first track they perform in a live set.
See more at Wikipedia.org...

Adjective
1. riding without a saddle; "a bareback rider"
(synonym) barebacked
(similar) unsaddled
Adverb
1. without a saddle; "she prefers to ride her horse bareback"
(synonym) barebacked

(adv.)
On the bare back of a horse, without using a saddle; as, to ride bareback.
  

Tractor without its semitrailer. (ATA1)