Source : Webster's Revised Unabridged Dictionary (1913)

Troth \Troth\, n. [A variant of truth. See {Truth}.]
   1. Belief; faith; fidelity.

            Bid her alight And hertroth plight.   --Shak.

   2. Truth; verity; veracity; as, by my troth. --Shak.

            In troth, thou art able to instruct gray hairs.
                                                  --Addison.

   3. Betrothal.

Source : WordNet®

troth
     n 1: a mutual promise to marry [syn: {betrothal}, {engagement}]
     2: a solemn pledge of fidelity [syn: {plight}]