say it: AL-tuh-tood
altitude is a noun meaning "elevation especially above sea level or above the earth's surface". It carries 3 recorded senses.
the perpendicular distance from the base of a geometric figure to the opposite vertex (or side if parallel)
angular distance above the horizon (especially of a celestial object)
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 altitude 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.