συμπληρόωsymplēróō

to implenish completely, i.e. (of space) to swamp (a boat), or (of time) to accomplish (passive, be complete)

Greek (New Testament) · G4845

Meanings

1. to fill up completely: of a ship filling with water, and by by metonymy, of those on board, Luke 8:23.

2. to complete, fulfil: of time (Jeremiah 25:12, and see MM, xxiv), Luke 9:51, Acts 2:1.

Same root

σύνsýn · G4862with or together (but much closer than G3326 (μετά) or G3844 (παρά)), i.e. by association, companionship, process, resemblance, possession, instrumentality, addition, etc.
πληρόωplēróō · G4137to make replete, i.e. (literally) to cram (a net), level up (a hollow), or (figuratively) to furnish (or imbue, diffuse, influence), satisfy, execute (an office), finish (a period or task), verify (or coincide with a prediction), etc.

Where it appears

Appears 3 times in the Bible.

Luke 8:23 As they sailed across, Jesus settled down for a nap. But soon a fierce storm came down on the lake. The boat was filling with water, and they were in real danger.
Luke 9:51 As the time drew near for him to ascend to heaven, Jesus resolutely set out for Jerusalem.
Acts 2:1 On the day of Pentecost all the believers were meeting together in one place.

Source: G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), public domain.