1 Kings 1:25
For he is gone down this day, and hath slain oxen and fat cattle and sheep in abundance, and hath called all the king’s sons, and the captains of the host, and Abiathar the priest; and, behold, they eat and drink before him, and say, God save king Adonijah.
On that day Adonijah went down and slew oxen and fat cattle and sheep in abundance for a feast. He called together all the king's sons and the captains of the host and Abiathar the priest to be with him. They ate and drank before him while acclaiming him with the cry, God save king Adonijah.
The gathering was a public display that he had organized influential supporters to seize the throne for himself. It was a rebellious attempt to establish himself as king contrary to God's appointment of Solomon.