Definition
An operational definition describes a behavior so two independent observers can agree on whether it occurred. It includes the topography, onset, offset, and a few examples and non-examples.
Vague definitions like aggression or non-compliance break interobserver agreement and make data uninterpretable. Operationally defining the target is the first step of any FBA or BIP.
Example
Aggression: any contact between the client's open or closed hand and another person's body, with audible impact, lasting less than two seconds. Onset is the moment of contact; offset is the moment of release.