12
traditional(adjective, state, quality, fashion, usual)
11
old(adjective, usual, last, past, conventional)
10
primeval(adjective, last, original, old, outdated)
8
olden(adjective, original, old, primitive, venerable)
7
dateless(adjective, lasting, permanent, everlasting, unending)
7
prehistoric(adjective, old, ancient)
6
age-old(adjective, last, original, old, outdated)
6
antediluvian(adjective, last, original, primitive, venerable)
6
timeless(adjective, vast, lasting, infinite, permanent)
5
ancient(adjective, new)
5
antique(adjective, last, original, primitive, venerable)
5
eternal(adjective, pause, endless, infinite)
5
rooted(adjective, old, ancient, oldness)
5
time-honored(adjective, old, ancient)
5
venerable(adjective, original, past, primitive, outdated)
4
archaic(adjective, last, original, old, venerable)
4
ceaseless(adjective, infinite)
4
customary(adjective, oldness)
4
early(adjective, last, original, primitive, venerable)
4
endless(adjective, infinite)
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APASmart Define. (2016). immemorial thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/immemorial/thesaurus/synonyms
ChicagoSmart Define. 2016. "immemorial thesaurus" https://smartdefine.org/immemorial/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2016, immemorial thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/immemorial/thesaurus/synonyms>.
MLASmart Define. "immemorial thesaurus" 29 February 2016. Web. 22 September 2026. <https://smartdefine.org/immemorial/thesaurus/synonyms>