  We stress some of the major differences between supergalactic winds and giant
superbubbles evolving into the giant low density haloes of galaxies. We review
major properties of bursts of star formation and the critical energy required
for mass ejection both in the case of an ISM strongly flattened by rotation and
that imposed by a more extended ISM distribution arising from a smaller
rotation. The limits are thus establish for galaxies with an ISM mass in the
range 10$^6$ M$_\odot$ to more than 10$^9$ M$_\odot$, and are compared with a
sample of local galaxies. Some of these galaxies seem to be above the critical
limit despite the fact that their structure is clearly that of a superbubble.
True supergalactic winds, as evidence by M82, are shown to exceed the critical
limit by more than an order of magnitude and thus the limit derived by Silich &
Tenorio-Tagle (2001) for mass ejection should be regarded as a lower limit.
