Is Upekṣā (equanimity) a feeling or simply numbness?

Is Upekṣā (equanimity) a certain kind of feeling which if attained, everyone will feel in a similar way, or its a kind of numbness to sensory input? From the wiki the definition of equanimity says > is a state of psychological stability and composure which is > undisturbed by experience of or exposure to emotions, pain, or other > phenomena It is not clear to me, as a Brahmavihara, is it a special kind of feeling, or it simply is maintaining calm composure in all circumstances,kind of indifference attitude, but this sounds like if practiced, is certain kind of numbness to sensory input, meaning, no matter what is the sensory input is, you stop or repress any kind of feeling that may arise.