cross

Definition:

In Bible times, a cross was an upright wooden post stuck into the ground, with a horizontal wooden beam attached to it near the top.

During the time of the Roman Empire, the Roman government would execute criminals by tying or nailing them to a cross and leaving them there to die.
Jesus was falsely accused of crimes he did not commit and the Romans put him to death on a cross.
Note that this is a completely different word from the verb "cross" that means to go over to the other side of something, such as a river or lake.

This term could be translated using a term in the target language that refers to the shape of a cross.
Consider describing the cross as something on which people were killed, using phrases such as "execution post" or "tree of death."
Also consider how this word is translated in a Bible translation in a local or national language. (See: How to Translate Unknowns)

40:01 After the soldiers mocked Jesus, they led him away to crucify him. They made him carry the cross on which he would die.
40:02 The soldiers brought Jesus to a place called "the Skull" and nailed his arms and feet to the cross.
40:05 The Jewish leaders and the other people in the crowd mocked Jesus. They said to him, "If you are the Son of God, come down from the cross and save yourself! Then we will believe you."
49:10 When Jesus died on the cross, he received your punishment.
49:12 You must believe that Jesus is the Son of God, that he died on the cross instead of you, and that God raised him to life again.