2
serious
2
severe
2
smart
2
sober
2
solemn
2
staid
2
thoughtful
2
valid
1
cute
1
dignified
1
discerning
1
good
1
heavy
1
nimble
1
sage
1
serious-minded
1
somber
1
strong
1
unfrivolous
1
well-advised
11 years ago|1.4k views|share |citing 
APASmart Define. (2015). harebrained thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/harebrained/thesaurus/antonyms
ChicagoSmart Define. 2015. "harebrained thesaurus" https://smartdefine.org/harebrained/thesaurus/antonyms (accessed September 22, 2026).
HarvardSmart Define 2015, harebrained thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/harebrained/thesaurus/antonyms>.
MLASmart Define. "harebrained thesaurus" 14 April 2015. Web. 22 September 2026. <https://smartdefine.org/harebrained/thesaurus/antonyms>