The Collaborative International Dictionary of English v.0.48:
Custom \Cus"tom\ (k[u^]s"t[u^]m), n. [OF. custume, costume,
Anglo-Norman coustome, F. coutume, fr. (assumed) LL.
consuetumen custom, habit, fr. L. consuetudo, -dinis, fr.
consuescere to accustom, verb inchoative fr. consuere to be
accustomed; con- + suere to be accustomed, prob. originally,
to make one's own, fr. the root of suus one's own; akin to E.
so, adv. Cf. Consuetude, Costume.]
1. Frequent repetition of the same act; way of acting common
to many; ordinary manner; habitual practice; usage; method
of doing or living.
And teach customs which are not lawful. --Acts xvi.
Moved beyond his custom, Gama said. --Tennyson.
More honored in the breach than the observance.
2. Habitual buying of goods; practice of frequenting, as a
shop, manufactory, etc., for making purchases or giving
orders; business support.
Let him have your custom, but not your votes.
3. (Law) Long-established practice, considered as unwritten
law, and resting for authority on long consent; usage. See
Usage, and Prescription.
Note: Usage is a fact. Custom is a law. There can be no
custom without usage, though there may be usage without
4. Familiar aquaintance; familiarity. [Obs.]
Age can not wither her, nor custom stale
Her infinite variety. --Shak.
Custom of merchants, a system or code of customs by which
affairs of commerce are regulated.
General customs, those which extend over a state or
Particular customs, those which are limited to a city or
district; as, the customs of London.
Syn: Practice; fashion. See Habit, and Usage.