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

A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.

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.