Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
longitudinally is an adverb meaning "across time". It carries 3 recorded senses.
across time
“We studied the development of the children longitudinally”
in the direction of the length
“He cut the paper lengthwise”
with respect to longitude
“longitudinally measured”
Definitions, synonyms and semantic relations for longitudinally come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.