The word "proxy" can mean more than one thing:

• a person authorized to act for another person, or upon request by another person (see eg.: Proxy murder)
• a political or business proxy representative
• a proxy war is a war where two powers use third parties as a substitute for fighting each other directly.
• a networking server: proxy server
• a design pattern called proxy pattern
• a measurement used in social science surveys or other research as an approximation to a desired measure that is impossible or inconvenient to obtain
• in climate research, a proxy is a measured variable used to infer the value of a variable of interest.
• in collectable card games, a card (usually a cheap or common one) that is marked so as to represent another card (usually a hard-to-get or expensive one). This is illegal in most tournaments, and often disapproved of in casual play.