ultraserious
adjective
ul·tra·se·ri·ous ˌəl-trə-ˈsir-ē-əs 
: extremely serious: such as
a
: very thoughtful or subdued in appearance or manner
wearing an ultraserious expression
b
: having exceedingly important or dangerous consequences
an ultraserious problem/injury
also : involving or deserving an exceedingly large amount of thought, attention, or work
an ultraserious topic
c
: not joking or funny
her ultraserious tone/expression
d
: extremely interested or devoted
an ultraserious student
e
: exceedingly great or impressive in quality, quantity, extent, or degree
an ultraserious piece of equipment
Word History
First Known Use
1851, in the meaning defined above