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1. the old one two
a video game combination of the melee attack and a shot from a shotgun or other gun with a deadly punch. Also commonly referred to as two-piecing after the destruction the victim suffers.
Fuck dude i fuckin' gave that bitch the old one two that noob got fuckin' two-pieced

oh shit, thats just embarassing
2. the old one two
1. death 2. finality 3. farewell 4. termination 5. destruction 6. killing 7. elimination 8. the dumping of a mate, partner, etc. 9. often sudden defeat 10. disposal 11. riddence (often used with 'give' in all contexts)
I just gave my girlfiend the old one two by showing her the front door for good. I gave the burglar the old one two with my side-by-side shotgun and he will never invade my home again. The older boy gave his little brother the old one two in a fistfight.
3. the old one two
Fingering a girl in her vagina starting off with one finger, preferrably the middle finger, and then leading it to using two fingers, typically the middle and index fingers.
Damn dude, I snuck in that fine ladies room last night, and it went down. We started just hangin' but it let to the old one two. Now she's beggin' me to hang.