There probably is an official definition but the stats I use look at the following:

Bombs (including: UVIEDs, RCIED, proxy and VOIED and ranging from small (pipe bombs) to large (500lb culvert bombs and bigger)).

Shoots

Hoaxes and criminality (even if conducted by Republican groupings) are not included. Rioting and paramilitary style 'civil-action' beatings are also not included.