Before any player casts a spell with the same name as a card in any graveyard, that player may say "sorry." If they don't, any other player may say "sorry" as the spell is being
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5). When another player says "sorry" this way,
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) the spell.
Whenever a player says "sorry" at any other time, Sorry deals 2 damage to that player.