Under: Refers to: over/under.
Underdog: Many refer to this as the “dog”. This is the team that is not expected to win the game.
Under the Gun:
1) Used in all card games to refer to the player seated directly to the dealer’s left side.
2) In Poker, refers to the player who should place the bet first.
Unit: The measure employed by all gambling players to set the size/amount of bet. Generally, 1 unit is the table’s minimum stake.
Unpaid Shill: A steady low roller.
Up a Tree: Used for a dealer’s face up card.
Upcard: The dealer’s exposed card in Blackjack.