In the Dungeons & Dragonsrole-playing game, a cantrip is a type of minor spell that generally is the simplest and weakest kind available to learn. Their weakness is usually described as they can only produce the magical effect equal to the energy put into it; no giant breaks from reality. ("Most cantrips are simple little spells of no great effect, so... knowledge and information pertaining to these small magics are discarded in favor of the more powerful spells when available.")[4] The differences, in terms of game mechanics, between cantrips and more powerful spells have changed from edition to edition.
In the trading card game Magic: The Gathering, a cantrip is player-jargon referring to a spell that, in addition to any other effect, makes a player draw a card.[5]
In the deck-building gameDominion, a cantrip is any Action card that is self-replacing: it both draws one card and gives an Action used to play it.[6]
References
Look up cantrip in Wiktionary, the free dictionary.
^Cantrip, Dictionary of the Scots Language (online edition).