(The). The vainglory, the ostentation, that which a person boasts of, or is proud of.
The boast of heraldry, the pomp of power, Awaits [sic] alike the inevitable hour.
Gray: The Elegy, stanza 9.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Boast from Infoplease: