Any specific article/author/group you'd recommend on the topic?
On the definition aspect:
Naylor, P., Cowie, H., Cossin, F., de Bettencourt, R., & Lemme, F. (2006). Teachers' and pupils' definitions of bullying.
British Journal of Educational Psychology, 76, 553-576. doi:
http://dx.doi.org/10.1348/000709905X52229
Kert, A. S., Codding, R. S., Tryon, G. S., & Shiyko, M. (2010). Impact of the word “bully” on the reported rate of bullying behavior.
Psychology in the Schools, 47(2), 193 – 204.
On the intervention aspect:
I know Scott Ross and Rob Horner are doing some really interesting work on this. AFAIK, they only have pilot data published so far, but I've spoken to Ross at conferences (super nice guy!), and it sounds like they have some really nice large scale replication data forthcoming.
Ross, S. W., & Horner, R. H. (2009). Bully prevention in positive behavior support
Journal of Applied Behavior Analysis,
42, 747-759. doi: 10.1901/jaba.2009.42-747.