bet one's bottom dollar
To be absolutely sure of something; to be certain enough of something to wager everything.
He talks about it a lot, but I would bet my bottom dollar that he has never actually been there.
ADJ
good, safe, sure | fair | outside
VERB + BET
have, make, place, put
My friends always make bets on who will win the football match each weekend.
accept, take
My friends wanted to accept my bet that the home team would win the championship.
win | lose
PREP
~ on
My friend lost money when she placed a bet on the wrong football team last weekend.
~ with
I placed a bet with my coworker on which team would win the match.
PHRASES
do sth for a bet, my bet is/it is my bet (that)
I think she'll arrive late, but that's just my bet on it.