An abbreviation of the word babys which is the misspelled version of babies and is used by scene kids who don't care about spelling or grammar, and the fact that we don't care when they post a bulletin about brushing their teeth or going to hang out with "mykulcurbcore" or "amendahxo".
Short for "baby" used when you don't want to use such an intimate word but still want to call them that.
ie. (Speaking to my new guy I'm dating but not my boyfriend yet) You're the best bby
By Meredithe
Bby
1. Abbreviation for baby. Also quite frequently might be a typo of "baby", since many people are not so lazy that they cannot type an extra letter.
2. Star Wars term used for calendar dates. Stands for "Before Battle of Yavin". Quite similar to BC in normal calendar date, which stands for "Before Christ".