'Headache' definitions:

Definition of 'headache'

From: WordNet
noun
Something or someone that causes anxiety; a source of unhappiness; "New York traffic is a constant concern"; "it's a major worry" [syn: concern, worry, headache, vexation]
noun
Pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs [syn: headache, head ache, cephalalgia]

Definition of 'Headache'

From: GCIDE
  • Headache \Head"ache`\ (h[e^]d"[=a]k`), n. Pain in the head; cephalalgia. "Headaches and shivering fits." --Macaulay. [1913 Webster]