surefire

今日の単語はReader's Digest １０月号の記事Energy Crisisからです。
Achieving a healthy weight will help boost energy levels, but be careful to pace your efforts: over-exercising and crash dieting are surefire ways to deplete your batteries even further.
"surefire" は知らない単語ですが、この単語も文脈から容易に意味を推測できます。しかし、確実にするために一応辞書で確認します。
・Merriam-Webster's Online Dictionary: certain to get successful or expected results: a surefire recipe
・Cambridge English Dictionary: certain or likely, especially to succeed: The film looks a surefire Oscar winner.: Running into the street like that is a surefire way to get hurt.
・Wiktionary: certain to work: That hat should be a sure-fire way to spot him in a crowd.