noun

• (idiomatic) Something insubstantial, fleeting, or transitory; unreal fancy; vain imagination; idle talk; boasting.
  "For what is your life? It is even a vapour, that appeareth for a little time, and then vanisheth away."
• (dated) Any medicinal agent designed for administration in the form of inhaled vapour.
  "Sulphurous fumes have also been recommended, as well as diffusing a variety of vapors in the apartment of the patient; on their beneficial or injurious effects we are unable to speak."
• (archaic, in the plural) Hypochondria; melancholy; the blues; hysteria, or other nervous disorder.
  "Jan 13, 1732, John Arbuthnot, letter to Jonathan Swift He talks me into a fit of vapours twice or thrice a week."
• (obsolete) Wind; flatulence.
  "The surcharge of the stomack from a gross vapour, and from the poise of some outward weight, are alike"

verb

• (intransitive) To become vapor; to be emitted or circulated as vapor.
• (transitive) To turn into vapor.
  "to vapor away a heated fluid"
• (intransitive) To use insubstantial language; to boast or bluster.
  "He vapoured, and fretted, and fumed, and trotted up and down, and tried to make himself pleasing in Miss Hollis's big, quiet, grey eyes, and failed."
• (transitive) To give (someone) the vapors; to depress, to bore.
  "“I only mean,” cried she, giddily, “that he might have some place a little more pleasant to live in, for really that old moat and draw-bridge are enough to vapour him to death […].”"