Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
deepness is a noun meaning "the intellectual ability to penetrate deeply into ideas". It carries 4 recorded senses.
the intellectual ability to penetrate deeply into ideas
the quality of being physically deep
“the profundity of the mine was almost a mile”
the extent downward or backward or inward
“the depth of the water”
“depth of a shelf”
“depth of a closet”
a low pitch that is loud and voluminous
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 deepness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.