Main adjectives are listed in this post. Each word below can often be found in front of the noun main in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing MAIN.
angry, atlantic, azure, billowy, blue, bounding
boundless, briny, de, distant, foaming, great
inch, la, lower, melancholy, mighty, northern
old, open, restless, roaring, solemn, southern
spanish, stormy, trackless, troubled, une, unshadowed
void, watery, western, wide, wintry
Hope this word list had the adjective used with main you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.