steer

Somebody who has (or has had) testicles, who is in a receiver/submissive role within castration, CBT or cuckolding play when that play does not involve feminization.

Whereas a Bull is a masculine-identifying, high-stamina person who engages in sexual topping or dominating, a steer is a masculine or non-binary identifying high-stamina person who inhabits either a submissive or victim role that may involve bottoming, or just receiving the castration play, CBT or cuckolding itself as the main focus of activity.

Steer derives from the American English name for a castrated bull, so has been adopted as an emasculated counterpart to that commonly-used kink terminology, with other symbolic characteristics remaining the same (e.g. strength and body-building).

Sometimes other duos of animal totems and their castrated counterparts are taken-on in this kind of kink play: ox (British English for steer), gelding (a castrated stallion), etc. Occasionally members of the Furry Fandom may also adopt roles associated with less well-known animals, and use wider vocabulary involving castration too.

The most common femme kink role adjacent to steer that commonly incorporates castration is sissy, where there is a symbolic role of enacting feminization (that is not in any way the case with steers).