1. (n.) A weapon (generally an assault rifle) chambered in 5.56 NATO caliber.
2. (adj.) of or in 5.56 NATO caliber.
1. "I count three hostiles: two AK's and a five-five-sixer, over."
2. The new five-five-sixer HE round was especially effective against lightly-armored vehicles and personnel.
Prices shown in USD.
Type your email address below to get our free Urban Word of the Day every morning!
Emails are sent from email@example.com. We'll never spam you.