Then Jesus says that we are in Him and He is in us. This question is really one addressing the idea of meaning. I argue that they change with the context. Words do not have any inherent meaning. All meaning is derived from association and relationship with other words.
Dictionaries only record the way in which words are used in different contexts.
We know that when Jesus declared that He was in the Father, and the Father was in Him, that this was a claim to deity. The Jews understood Him to be claiming to be God Himself. Jesus defended this understanding of theirs instead of denying it. Based on Jesus' prior use of this phrase, we have no reason to doubt that again He is claiming deity. He said that He was in the Father and the Father was in Him.