76 entries under smooth topic. ×

4
procumbent(adjective, flat, low, level)
4
upright(adjective, solid, level, true)
3
vertical(adjective, solid, level, true)
3
aligned(adjective, calm, flat, plain)
3
balanced(adjective, calm, direct, right)
3
calm(adjective, flat, plain, level)
3
erect(verb, adjective, solid, level)
3
linear(adjective, right, solid, level)
3
plumb(adjective, direct, right, flat)
3
steady(adjective, calm, quiet, right)
3
undeviating(adjective, quiet, direct, right)
2
alike(adjective, calm, direct, right)
2
continuous(adjective, calm, quiet, direct)
2
dead flat(expression, adjective, flat, even)
2
in line(expression, adjective, idiom, calm)
2
invariable(adjective, quiet, soft, gentle)
2
matching(adjective, calm, direct, right)
2
planate(adjective, calm, quiet, direct)
2
reclining(adjective, low, level, lying)
2
rolled(adjective, calm, flat, plain)
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APASmart Define. (2015). horizontal thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/horizontal/thesaurus/synonyms
ChicagoSmart Define. 2015. "horizontal thesaurus" https://smartdefine.org/horizontal/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, horizontal thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/horizontal/thesaurus/synonyms>.
MLASmart Define. "horizontal thesaurus" 10 April 2015. Web. 24 September 2026. <https://smartdefine.org/horizontal/thesaurus/synonyms>