Increase in gloss or sheen of paint film when subjected to rubbing, scrubbing or having an object brush up against it.
Possible Causes:
Use of flat paint in highly trafficked areas, where a higher sheen level would be desirable.
Frequent washing and spot cleaning. Objects (furniture, for example) rubbing against the walls.
Use of lower grades of paint with poor stain and scrub resistance (see Poor Stain Resistance and Poor Scrub Resistance).
Solution
Paint heavy wear areas that require regular cleaning (e.g., doors, window sills and trim) with a top quality latex paint, because this type of paint offers both durability and easier cleaning capability. In high traffic areas, choose a semigloss or gloss rather than a flat sheen level. Clean painted surfaces with a soft cloth or sponge and non-abrasive cleansers; rinse with clean water.
(image courtesy of The Rohm and Haas Paint Quality Institute)