BYT, a young team from bonnyrigg that are known to run away from fights

Noun: a friend who is usually only called upon by a friend when a more primary/prominent friend is unavailable.

Taken from the term “second string” in an athletic competition situation. In football, if the star quarterback gets injured during a play, the second string is called off the bench to replace him/her. A “Second String Friend” is essentially benched until needed, if ever.

Synonyms: Plan B, Second Choice, Secondary Friend, Benched Until Needed

BYT, or Bring Your own Trustfund, is a group of over privileged DC hipsters who try to make DC like Brooklyn because their parents will cut off their credit cards and trust funds if they actually move to Brooklyn.

Bitch You Thought, BYT. When a dumb bitch thinks or tries something she needs to rethink

"Bright Young Things", from the alternate title of Evelyn Waugh's 1930 novel Vile Bodies about affluent London glitterati/party-goers (a la Hiltons/Lohans but slightly less illiterate)

Now, via analogy to MJ hit "PYT" the abbreviation has been applied in a wider sense beyond celebutantes, to wit, the little valedictorian darlings from Stanvard or Yalumbia who see it as their birthright to be rulers & managers of the universe but lack information about other walks of life, have never lifted anything heavier than a bookbag or lacrosse stick, and are otherwise prestigious before their time. Often found at TED conferences, Park City trade conventions, in Barcelona/Prague/Copenhagen for years abroad, in the U.S. DOJ, or at their apartments watching Rachel Maddow, 30 Rock, True Blood, Deadwood, Big Love, Entourage (basically anything from the HBO Time Warner production office is catnip to them)

internet slang
"before your time"

The better known abbreviation for the Washington, DC based hipster organization and party promoters Brightest Young Things.