noun

• (countable, archaic) An oath, pledge, plight, or promise.
  "By my troth I care not, a man can die but once, we owe God a death, [...]"
• (countable, archaic) An oath, pledge, plight, or promise.
  "...I envy not the beast that takes His license in the field of time, Unfetter'd by the sense of crime, To whom a conscience never wakes; Nor, what may count itself as blest, The heart that never plighted troth But stagnates in the weeds of sloth;..."
• (countable, archaic) An oath, pledge, plight, or promise.
  "I did, therefore, what an honest man should; restored the maiden her troth, and departed the country, in the service of my king."
• (countable, uncountable, archaic) Truth; something true.
  "[John] Martiall, much like to Virgil's Sinon, (of whom he took a precedent, to make an artificial lie,) for three leaves together, in his preface, telleth undoubted trothes; to the end that the falsehoods, which, foolishly, (God wot,) he doth infer, may have the more credit."

verb

• (obsolete) To pledge to marry somebody.