bet one’s bottom dollar

bet your bottom dollar

Be certain that something will happen (so much so that one would hypothetically risk one's last dollar betting on it). I lost my umbrella, so you can bet your bottom dollar that it will rain tomorrow! Oh, you can bet your bottom dollar that Kevin will be late tonight—he's never on time!
See also: bet, bottom, dollar

bet one’s bottom dollar

tv. to be very certain of something; to bet in complete certainty of winning. (Need not refer to an actual bet.) I bet my bottom dollar you never ever went to Alaska!
See also: bet, bottom, dollar