1.
main, primary, central
The most important or prominent element among several. Used as a modifier before nouns.
Usage
メイン functions primarily as a noun modifier (メインの～ or メイン～). It is the standard way to say "main" in modern Japanese and is used much more frequently than its Japanese equivalent 主要な in casual speech.
Forms
The older spelling メーン (メーンストリート, メーンイベント) is still seen, especially in older newspaper style; メイン is now standard.