adj

• (predicative only) Feeling a sense of spinning in the head, causing a perception of unsteadiness and being about to fall down; dizzy.
  "The man became giddy upon standing up so fast."
• (attributive) Causing or likely to cause dizziness or a feeling of unsteadiness.
  "They climbed to a giddy height."
• (by extension)
  "The Biſhop, and the Duke of Gloſters men, / Forbidden late to carry any VVeapon, / Haue fill'd their Pockets full of peeble ſtones; / And banding themſelues in contrary parts, / Doe pelt ſo faſt at one anothers Pate, / That many haue their giddy braynes knockt out: […]"
• (by extension)
  "'E isn't one o' the reg'lar Line, nor 'e isn't one of the crew. / 'E's a kind of a giddy harumfrodite—soldier an' sailor too!"

noun

• (British, agriculture, veterinary medicine) Synonym of gid (“a disease caused by parasitic infestation of the brain by tapeworm larvae”).

verb

• (transitive) To make (someone or something) dizzy or unsteady; to dizzy.
  "A nevv faſhion of apparrell creepeth no ſooner into vſe, but preſently he blameth and diſpraiſeth the olde, and that vvith ſo earneſt a reſolution, and vniverſall a conſent, that you vvould ſay, it is ſome kinde of madnes, or ſelfe-fond humor, that giddieth his vnderſtanding."
• (intransitive)
  "Giddied, he gave up a moment's purchase of ground."
• (intransitive)
  "[B]y chance, a sudden north-wind fetch'd, / With an extreme sea, quite about again / Our whole endeavours, and our course constrain / To giddy round, and with our bow'd sails greet / Dreadful Maleia, calling back our fleet / As far forth as Cythera."