soda water

1. 1. See carbonated water.
   2. See soft drink.
2. A solution of water, sodium bicarbonate, and acid.

Artificially carbonated water, also known as club soda; if sodium bicarbonate is also added, the product is seltzer water.

Water that has been highly charged with carbon dioxide, which gives it effervescence. Soda water, also called club soda, seltzer water or just plain carbonated water, contains a small amount of sodium bicarbonate, which, because it's alkaline, can help neutralize an acidic stomach. Soda water is combined with sweeteners and flavorings to produce a variety of soft drinks. Many cocktails also use soda water as an ingredient. See also seltzer water.

The noun has 2 meanings:

Meaning #1: effervescent beverage artificially charged with carbon dioxide
  Synonyms: carbonated water, club soda, seltzer, sparkling water

Meaning #2: a sweet drink containing carbonated water and flavoring
  Synonyms: pop, soda, soda pop, tonic