Reckon/ˈrekən/ Definition 1 of 4Pro Tip 1/3Personal Belief Use 'reckon' to express a personal opinion or belief that's not formal or scientific. I reckon you'll enjoy the movie. Pro Tip 2/3Informal Agreement 'Reckon' is often used to show agreement in casual conversation. You reckon she'll come? Yeah, I reckon. Pro Tip 3/3Cultural Flavor 'Reckon' is commonly used in UK, Australia, and New Zealand, giving your English a regional feel. They reckon it's a true story.