Full Idea
The defining claim of adverbialism is that the contents of sense-experience are modes, not objects, of sensory activity.
Clarification
Adverbs show how you do something (e.g. 'quickly'); a 'mode' is a way of doing something
Gist of Idea
Adverbialism sees the contents of sense-experience as modes, not objects
Source
Howard Robinson (Perception [1994], VII.5)
Book Reference
Robinson,Howard: 'Perception' [Routledge 2001], p.175
A Reaction
This seems quite a good account of simple 'modes' like colour, but not so good when you instantly perceive a house. It never seems wholly satisfactory to sidestep the question of 'what are you perceiving when you perceive red or square?'