from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A nonalcoholic, flavored, carbonated beverage, usually commercially prepared and sold in bottles or cans.
- n. A serving of this beverage. See Regional Note at tonic.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any carbonated, usually sweet, non-alcoholic drink. (In this sense, juice, milk, tea and coffee are not soft drinks.)
- n. Any non-alcoholic drink.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. nonalcoholic beverage (usually carbonated)
So called in contrast to alcoholic beverages, which are "hard drinks". (Wiktionary)