It is mostly about the Lord’s Second Coming, but it also has other nuances that clarify the definition. What do two Greek lexicons say about it? A nontechnical article.
Parousia is pronounced pah-roo-see-ah
Bauer, Danker, Arndt and Gingrich were lexicographers who edited a Greek lexicon, considered by many to be the authoritative one of the Greek NT. It is abbreviated BDAG (slightly edited for clarity).
It defines the term in this way.
(1). “The state of being present at a place, presence.”
1 Cor. 16:17: Stephanus, Fortunatus, and Achaichus arrived.
Phil. 2:12: Paul calls the Philippians his beloved and reminds them to keep on obeying, not only when he is present with them, but in his absence.
2 Cor.10:10: Paul’s critics said his letters are weighty and strong, but his bodily presence is weak.
(2). “Arrival at the first stage in presence, coming, advent.”
a.. Of human beings in a normal sense.
2 Cor. 7:6-7 Paul was comforted by the coming of Titus, used twice.
Phil. 1:26: Paul promises that the Philippians may have ample cause to glory in Christ Jesus, because of his coming to them again. BDAG offers another translation of coming: return.
b.. In a special technical sense:
It was the presence of a divinity “who makes his presence felt by the revelation of his power or whose presence is celebrated in the cult” (religion).
BDAG offers no biblical references, but it is clear that the presence of the divinity visits the religious service.
On the other hand, Parousia “became the official term for a visit of a person of high rank, especially of kings and emperors visiting a province.”
“These two technical expressions can approach each other closely in meaning, can shade off into one another, even coincide.”
aa.. “Of Christ, and nearly always of his Messianic Advent in his glory to judge the word at the end of the age”:
Matt. 24:3; 1 Cor. 1:8; 15:23; 2 Thess. 2:8; 2 Pet. 3:4; 1 John 2:28; Matt. 24:27, 37, 39. 1 Thess. 4:15; Jas. 5:7; 1 Thess. 3:13; 2:19; 5:23; 2 Thess. 2:1; 2 Pet. 3:12
bb.. In early Christian writing outside the NT, it often referred to Christ’s advent in the Incarnation.
cc.. It can also refer to the coming of the Antichrist.
2 Thess. 2:9
Liddell and Scott were classical lexicographers (they studied broader ancient Greek literature), and they say it is related to the verb pareimi (eimi– is the verb to be and the entire word is pronounced pah-ray-mee, and para means “close beside”). They define this verb as follows:
Of persons or people
(1). “To be by or present”
(2). “To be present in or at a thing”
(3). “To be present so as to help, stand by”
(4). “To arrive at, to have come to, a place”
In all of these cases the person is right there, arrived on the scene.
In Scripture parousia refers to the arrival and coming of an individual like Paul or the Lord himself. And the coming was bodily or it was rarely used in a cultic sense of a religion of presence, outside the NT. The NT writers used the term for the arrival and bodily coming of the Lord, like an emperor or king arriving on the scene. When he does, it was a “game-changer” or it ushered in a new age, with God through his Messiah ruling and reigning and judging the world. It took on a more technical meaning for the Lord’s arrival. It could be translated in some contexts as visitation, which is how commentator R. T. France translates it in his commentary on Matthew (p. 895, note 14).
Of special interest to the NT is the meaning of a king or emperor arriving in a province. More research says that the people went out to greet the king or emperor and escorted him into the capital city or administrative center.
It is not likely that he arrived and instantly got back in his ship and sailed off with the dignitaries who went out to meet him.
Evidently, parousia does not mean that the Lord snatched people away and disappeared with them. Instead, the king or emperor stayed with the people at his destination, the capital.
Likewise, when the Lord returns, he will not disappear with them and “sail back” into heaven with his people who went into the air to meet him. Instead, he will come back with them and they will escort him to his destination–earth.