The “Play to Kill” mechanic is common in trick-taking games, although it may have slightly different meanings. In general, play-to-kill is a rule where you must try to win the trick if possible.
Play-to-kill is frequently required for games with trump suits. In this case, there is typically a lead suit for each trick, and you must play the lead suit if you can. However, if you do not have a card in the lead suit, but you do have a card in the trump suit, then you must play a card of the trump suit. Additionally, if you have a card that will take the trick, you must play it regardless of whether you have other cards that meet the usual play criteria but would not take it. This is the way play-to-kill works in Pinochle.
Related Term: A “slough” is a play that is guaranteed NOT to take the trick at the time you play it.
In poker, you may see a “Kill Hand” triggered, which forces some lucky player to make a large blind bet. This mechanism is intended to curb reckless betting that wins by pure luck. As a group, we will not implement “Kill Hands” in our poker games until we are all experienced enough to unanimously agree on the need. If you wish to read more about this particular poker mechanic, you can do so at Wikipedia.