Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
runniness is a noun meaning "the property of flowing easily". It carries one recorded sense.
the property of flowing easily
“adding lead makes the alloy easier to cast because the melting point is reduced and the fluidity is increased”
“they believe that fluidity increases as the water gets warmer”
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 runniness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.