"Nibiru (also transliterated Neberu, Nebiru) is a term in the Akkadian language, translating to "crossing" or "point of transition", especially of rivers[1], i.e. river crossings or ferry-boats. In Babylonian astronomy, nibiru (in cuneiform spelled dné-bé-ru or MULni-bi-rum) is a term of the highest point of the ecliptic, i.e. the point of summer solstice, and its associated constellation. The establishment of the nibiru point is described in tablet 5 of the creation epic Enûma Eliš""

Then you have the interpretation by Zecharia Sitchin that Niburu is a planet in a big elliptical orbit around the sun.

Well Sitchin is a Freemason and a proffesional deciever so I would not put much trust in what he writes.

The babylonian concept of "crossing" or "transition" is closer to the truth I think. It can be the moment when heaven and earth collide which menas the heavenly merges with earthly. Satan and his angels are cast down to earth to carry out God's wrath in the end times tribulation.