3
old(adjective, continue, customary, hardened, traditional)
3
persisting(adjective, persistent, continuous, hardened, lasting)
3
remaining(adjective, persistent, lasting)
2
aged
2
immemorial(adjective, old, ancient)
2
long-established(adjective, existing)
2
long-term
2
rooted(fixed, persistent, customary, traditional, lasting)
2
seasoned
2
time-honored(adjective, customary)
2
time-honoured
2
tough(steady, even, unchanging)
2
venerable
1
acknowledged
1
admitted
1
age-long
1
ancient
1
antique
1
confirmed(complete, true, fixed, persistent, hardened)
1
continual(persistent, continuous, lasting, continuing, remaining)
11 years ago|2.3k views|share |citing 
APASmart Define. (2015). long-standing thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/long-standing/thesaurus/synonyms
ChicagoSmart Define. 2015. "long-standing thesaurus" https://smartdefine.org/long-standing/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, long-standing thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/long-standing/thesaurus/synonyms>.
MLASmart Define. "long-standing thesaurus" 10 April 2015. Web. 24 September 2026. <https://smartdefine.org/long-standing/thesaurus/synonyms>