say it: hawr-ti-KUHL-chur-ist
horticulturist is a noun meaning "an expert in the science of cultivating plants (fruit or flowers or vegetables or ornamental plants)". It carries one recorded sense.
Forms marked are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for horticulturist come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.