At my games, a muck is as follows:
- If cards are thrown in a forward manner outside of a player's immediate playing area, and both cards land face up on a "live" portion of the table (which includes the board but does not include the muck pile or chip rack), that is not a muck.
- Any other forward motion is a muck
- Any cards that are touched by the dealer in any way are mucked
- A verbal announcement of a fold causes those cards to be mucked