Initialism of international reply coupon.
"The postal worker explained that she needed to purchase an IRC to cover the return postage when sending a letter abroad."
In plain English: IRC is an old internet chat system where people type messages to talk instantly with others online.
"Many people preferred to chat on IRC rather than use email for quick conversations."
To participate in Internet Relay Chat.
"She spent hours ircing with strangers from around the world to discuss her favorite books."
In plain English: To irc means to send messages on an online chat room called IRC.
"Please irc me your location so we can meet up at the park."
Initialism of Internet Relay Chat.
"Many users joined IRC to chat in real time on their favorite servers."