Whereas some manufacturers talk about the dielectric breakdown level of insulation between the core windings, others refer to the point at which certain equipment(ie. generators begin to consume rather than produce energy.

Yes, the actual proper term is

"Basic Impulse Insulation Level"

And are often abbreviated with one or the other.

Transformer Basics Chapter 1 (http://www.federalpacific.com/university/transbasics/chapter5.html)