n. The cardinal number equal to 8 + 1.n. The ninth in a set or sequence.n. Something having nine parts, units, or members.n. Games A playing card marked with nine pips.n. A set of nine persons or things, especially:n. Baseball The nine players on a side, or the whole team.n. Greek Mythology The nine Muses.n. A size, as in clothing or shoes, designated as nine.n. Sports The first or second 9 holes of an 18-hole golf course.idiom. to the nines Informal To the highest degree: dressed to the nines.