Full Idea
Sense-data are that which is given to us directly and immediately such as colour, shape, smell, without identification of them as specific material objects; they are usually thought to be devoid of judgment, interpretation, bias, preconception.
Gist of Idea
Sense-data are neutral uninterpreted experiences, separated from objects and judgements
Source
Peter A. Angeles (A Dictionary of Philosophy [1981], p.254)
Book Reference
Angeles,Peter A.: 'A Dictionary of Philosophy' [Harper 1981], p.254
A Reaction
This definition makes them clearly mental (rather than being qualities of objects), and they sound like Hume's 'impressions'. They are not features of the external world, but the first steps we make towards experience.