Synonyms for Headache:

n.

necessity, mare, the elephant in the room, chore, a tall order, struggle, task, megrim, the impossible. electric shock, bellyache, problem, jumble, mess, eyestrain, growing pains, difficulty, backache, charley-horse, colic. onus, burden, over, millstone, weight, heavy, tax. aggravation (noun)
irritation, difficulty, affliction, head ache, pain, distress.
bad news (noun)
struggle, grief, concern, problem, torment, mess.
bother (noun)
bellyache.
cognition (noun)
vexation, concern, worry.
distress (noun)
malaise, anguish, throe, ache, suffering, misery, pang, discomfort, torture.
headache (noun)
vexation, concern, cephalalgia, megrim, worry, head ache.
misery (noun)
agony, stitch.
pain (noun)
grief, painfulness, agony, wound, cramp, stitch, misery, gripe, bite, ache, sting, earache, bruise, affliction, discomfort, malaise, torment, inflammation, spasm, pang, Migraine, distress, Back Ache, smarting, suffering, torture, throe, throb, irritation, infliction, stab, hurt, rack, anguish, chafing, injury, wrench, pain, crick, burn, sore.

Other synonyms:

necessity, struggle, task, mare, onus. difficulty. millstone. tax. burden. weight. Other relevant words:
difficulty, chore, concern, head ache, cephalalgia, tax, weight, millstone, bellyache, heavy, problem, task, colic, worry, onus, backache, megrim, necessity, vexation, burden.

Usage examples for headache

  1. If it weren't for this headache I'd do it today." – Out of the Air by Inez Haynes Irwin
  2. And I hope to heaven you already had a headache – The Two Vanrevels by Booth Tarkington
  3. I have a horrid headache – The Aspirations of Jean Servien by Anatole France