I think it means a feeling that isn't particularly pleasant or unpleasant, but just neutral. For example, if you put your hand on the table, it feels like a table top. (As opposed to, say, the unpleasant feeling of putting your hand on a hot stovetop burner, or the pleasant feeling of putting your hand on a warm kitten.)
But, no, this has nothing at all to do with indifference. Neutral feelings can be very engaging.
Just my 2 cents ...
Venerable Mahasi Sayadaw has used the word indifference to desrcribe equanimity. Indifference is not always used in the negative.
The expression "Brahmavihara", if analysed, will include metta, friendliness or loving-kindness, karuna, compassion, mudita, goodwill or rejoicing with others in their happiness or prosperity, and upekkha, equanimity or indifference to pain and pleasure. These are the four kinds of Brahmavihara. http://www.buddhanet.net/brahmaviharas/bvd002.htm
This is our foundation: to have sati, recollection, and sampajañña, self-awareness, whether standing, walking, sitting, or reclining. Whatever arises, just leave it be, don't cling to it. Be it like or dislike, happiness or suffering, doubt or certainty... Don't try to label everything, just know it. See that all the things that arise in the mind are simply sensations. They are transient. They arise, exist and cease. That's all there is to them, they have no self or being, they are neither ''us'' nor ''them.'' They are not worthy of clinging to, any of them. - Ajahn Chah