Definition of: combination

(kom′bə·nā′shən) noun
1. A joining together; union; alliance.
2. A compound or group.
3. plural Underwear made in one piece.
4. The series of numbers or letters forming the key symbol to a keyless lock or combination lock; also, the mechanism operated by such a sequence.
5. Math. A group of several things or symbols in which the order of arrangement is immaterial.
6. Chem. The union of elements in certain fixed proportions, or the compound thus resulting.
7. An alliance of politicians, or merchants, etc., to protect or further a common interest, activity, or advantage.
8. An alliance of corporations; a combine or monopoly.
9. A railroad car divided into a baggage and a passenger section. See synonyms under CABAL, UNION. [<MF <LL combinatio, -onis a joining by twos <combinare. See COMBINE.]
—com′bi·na′tion·al adjective