Never having lost a game, battle, or competition; remaining victorious throughout.
Combination of prefix 'un-' (not) and 'defeated' (past participle of defeat, from Old French 'defaire' meaning to undo). The word emerged in English to describe sustained victory.
Being undefeated is rarer than you'd think—even the most dominant teams in sports history have eventual losing streaks, which is why undefeated seasons (like the 1972 Miami Dolphins in NFL) become legendary and are talked about for decades.
Complete word intelligence in one call. Free tier — 50 lookups/day.