What is the meaning of the word "ice-cream soda"?

Definitions:

A carbonated beverage mixed with ice cream and flavored syrup. NOUN
- She ordered a chocolate ice-cream soda with extra whipped cream on top.
A cold drink consisting of ice cream served in a glass with flavored sode water or another soft drink. NOUN
- The classic ice-cream soda is a nostalgic treat from old-fashioned soda fountains.