Put the meaning into your own words.

It was presumptuous to announce an agreement before the others had approved it.

Later, a committee member wrote a sycophantic introduction that lavishly praised the donor's taste in hopes of gaining personal favor. During rehearsal, he became patronizing toward a capable designer, explaining simple tasks as though she could not understand her own work. He also made a presumptuous promise that the gallery next door would lend its largest room, although its manager had given him no authority to offer it.