And on the first day of Unleavened Bread, when they killed the Passover lamb, his disciples said to him, “Where will you have us go and prepare for you to eat the Passover?”
Mark 14:12

Frequently, when we talk about "Passover", we mean either the day before Unleavened Bread begins or else the full week of Unleavened Bread. However, the word Passover also frequently (and more technically) refers to the lamb itself, rather than to a holiday. This might seem nitpicky, but it's important for understanding some texts.

In the first part of this verse, "Killed the Passover" refers to the lamb, not to the ritual or the day. So in the second part, "eat the Passover" also refers to the lamb, not to matzo or a seder or some other special meal. Yeshua's disciples killed a Passover lamb and ate it with him the night before he was crucified.