day one
In real, traceable use. Part of the curated seed collection; community review is coming.
Meaning · English
A close, longtime friend, one who has been around since the beginning.
Register: slang
Where it’s used:
Used
American English
Examples
Raise a cup up for all my day ones; two middle fingers for the haters […]
Usage example from English Wiktionary (CC BY-SA 4.0, retrieved 2026-07-30)
Sources & notes
Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-07-30 via kaikki.org).
Common questions
What does “day one” mean?
A close, longtime friend, one who has been around since the beginning.
Is “day one” formal or informal?
day one is generally slang.