1. Noun. A planet in Mass Effect where you must sacrifice one of two squadmates, Kaidan Alenko or Ashley Williams. Other notable events include an encounter with main villains Saren and Sovereign, the detonation of a nuclear bomb, and the possible death of Urdnot Wrex, another squadmate.
2. Verb. The act of sacrificing someone on Virmire.

When you eat dirt for the first time and leave your family to build a shack in the woods