Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
heliometer is a noun meaning "an instrument used to measure the angular separation of two stars that are too far apart to be included in the field of view of an ordinary telescope". It carries one recorded sense.
an instrument used to measure the angular separation of two stars that are too far apart to be included in the field of view of an ordinary telescope
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 heliometer come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.