bye

bye is a Noun

Definition:

[1] A thing not directly aimed at; something which is a secondary object of regard; an object by the way, etc.; as in on or upon the bye, i.e., in passing; indirectly; by implication. [Obs. except in the phrase by the bye.] The Synod of Dort condemneth upon the bye even the discipline of the Church of England. Fuller.

[2] A run made upon a missed ball; as, to steal a bye. T. Hughes. By the bye, in passing; by way of digression; apropos to the matter in hand. [Written also by the by.]