The word falleciste is the preterite form of fallecer in the second person singular. There are other translations for this conjugation.

fallecer

Examples

¿En qué año falleciste?	What year did you cross over?
¿Recuerdas cuando falleciste? Si.	Remember when you diedcin that car accident? Yeah.
Amaste la Cruz, la cargaste incansablemente, la adoraste regularmente, a sus pies en el Krizevac, y allí falleciste.	You loved the cross, you carried it untiringly, you venerated it regularly and you breathed your last breath at the foot of the cross on Friday on Križevac.
Falleciste antes que nosotros lo hiciéramos, pero nunca te olvidaremos.	You passed away before we did, but we will never forget you.
No lo entiendo. Falleciste.	I don't understand that.