Mill

Mill in Collective
Mill is an approved shorthand for the effect of moving cards from the top of a deck to that player's graveyard.

Mill in other games
Mill is a term which originated in Magic: the Gathering to refer to an effect which moves cards from the top of a players library into their graveyard for the purpose of reducing the size of your opponent's deck as an alternate win condition. Over time this was expanded in various ways across many games.

Magic: the Gathering's term Mill can also refer to the effect of removing cards from your opponent's deck from the game for the same purpose of achieving an alternate win condition. Over time, archetypes like "Self Mill" also became popular.

In other card games, Mill has an expanded meaning. Hearthstone's use of Mill usually relates to forcing an opponent to draw too many cards, instead of directly placing them in the discard pile. Shadowverse has a similar definition.

Yu-Gi-Oh has mill strategies as well, which include a mix of MTG-style direct milling and Hearthstone-style forced card draw, as well as effects which change the opponents cards to the defensive position to stall out games.

Eternal Card Game has many MTG-style mill effects.

Overall, mill effects are disproportionately and inversely powerful related to deck size, and for this reason games with relatively small deck sizes compared to MTG, like Hearthstone (which has 30 card decks), are much less likely to use the "original definition of mill." Eternal Card Game has 75 card decks, so its mill cards are very close to the "original definition." This is one reason why games with deck sizes in between Hearthstone and MTG, like Yu-Gi-Oh, have a mix of Hearthstone and MTG styles of mill strategies.