/fif"tee fif"tee/ , adj.
1. equally good and bad, likely and unlikely, favorable and unfavorable, etc.: a fifty-fifty chance of winning.
adv.
2. in an evenly or equally divided way: The board voted fifty-fifty on the merger.
3. go fifty-fifty (on) , to share equally in the cost, responsibility, or profits (of): We went fifty-fifty on the dinner check.
Also, 50-50 .
[ 1910-15, Amer. ]