Resolute or strenuously active.
Excellent, very good.
Exceedingly violent, severe, ferocious, cruel or savage.
Of exceptional quality, exhibiting boldness or chutzpah.
Threatening in appearance or demeanor.
Extremely; very.
That operates to produce an effect.
Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment.
An operative person or thing.