CFAR's 2019 workshop participant handbook defines an aversion as
any sort of mental mechanism that causes us to be less likely to engage in a particular activity, or to do so only with pain, displeasure, or discomfort. Aversions can be conscious or unconscious, reasoned or felt, verbal or visceral, and they can range anywhere from a slight tinge of antipathy to outright phobias.
Aversion factoring is goal factoring for aversions: trying to understand why you're averse to a particular thing by decomposing it into underlying preferences and experiences.
Aversions make us less likely to engage in "activities," and as Scott Alexander's (2011) Physical and Mental Behavior notes, this includes mental as well as physical activities. Pavlovian conditioning can cause humans to unconsciously flinch from even thinking about a serious personal problem they have.
Writing in 2010, Roko introduced the term ugh field to refer to this problem:
If you fail or are punished sufficiently many times in some problem area, and acting in that area is always [preceded] by thinking about it, your brain will propagate the psychological pain right back to the moment you first begin to entertain a thought about the problem, and hence cut your conscious optimizing ability right out of the loop.
[...] The subtlety with the Ugh Field is that the flinch occurs before you start to consciously think about how to deal with the Unhappy Thing, meaning that you never deal with it, and you don't even have the option of dealing with it in the normal run of things. I find it frightening that my lizard brain could implicitly be making life decisions for me, without even asking my permission!
The ugh field forms a self-shadowing blind spot covering an area desperately in need of optimization.