The percentage of trades that result in profit. A 55% win rate means 55 out of 100 trades are winners.
Win rate is meaningless without context. A 90% win rate with 1:0.1 RR (risking $10 to make $1) is actually unprofitable — 10 wins make $10, but 1 loss costs $10, netting $0. Most consistently profitable traders have win rates between 45-65% with RR ratios above 1:1. In prop trading, a lower win rate with higher RR is generally safer because it reduces the probability of long losing streaks that breach drawdown limits.