say it: HED-ayk
headache is a noun meaning "something or someone that causes anxiety; a source of unhappiness". It carries 2 recorded senses.
pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs
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 headache 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.