a.
1.
Grave, solemn, sedate, staid, sober, earnest, demure.
2.
Important, weighty, great, momentous, grave.
3.
In earnest.
4.
Dangerous.
SERIOUS
Meaning of SERIOUS in English
Soule. Dictionary of English synonyms. Словарь английских синонимов. 2012
a.
1.
Grave, solemn, sedate, staid, sober, earnest, demure.
2.
Important, weighty, great, momentous, grave.
3.
In earnest.
4.
Dangerous.
Soule. Dictionary of English synonyms. Словарь английских синонимов. 2012