As a noun upburst
is the act of bursting upwards; a breaking through to the surface; an upbreak or uprush; as, an upburst of molten matter.
As an adjective unburst is
not having burst.
upburst
English
Noun
(
en noun)
The act of bursting upwards; a breaking through to the surface; an upbreak or uprush; as, an upburst of molten matter.
unburst
English
Adjective
(-)
Not having burst.