“Spirit-filled” is a phrase popularized by the charismatic renewal movement in the 70’s and 80’s. It generally means that the person described that way has been filled with or by, or baptized in or by the Holy Spirit, usually considered verified if the person has spoken in tongues.
There isn’t an orderly theological presentation in Scripture about the technicalities of being filled with the Spirit or baptized in or by or with the Spirit. Just the fact that the process is described with several different phrases creates difficulty in discussing it.
One day, after the cross, Jesus breathed on His disciples and told them to “receive the Holy Spirit.” (John 20:22)
In Acts chapter 2, on the day of Pentecost, everybody in the upper room was filled with the Spirit.
In Acts chapter 4, while leaders were praying for Jesus to confirm His words with signs and wonders as they preached, everyone who was present was filled with the Spirit.
Each time, there were people present who had not been at the earlier meetings. Each time, it is likely there were people present who had been at each meeting. I deduce from these facts that we should be filled at every opportunity.