Boast adjectives are listed in this post. Each word below can often be found in front of the noun boast in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing BOAST.
chief, common, constant, empty, false, famous
favorite, favourite, foolish, frantic, glorious, great
greatest, highest, idle, just, least, little
longer, many, mere, much, national, old
only, own, peculiar, proud, proudest, same
solitary, special, such, vain, vainglorious
Hope this word list had the adjective used with boast you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.