With 11 minutes remaining in the fourth quarter and the Thunder leading 75-65, Adams surprised Hamilton with a little hip-check as Oklahoma City transitioned from a defensive rebound into an offensive possession. Responding to the bump from Adams, Hamilton swung a closed right fist into Adams' chest, making minimal contact, and the two players continued up the court as if nothing had happened. The referees intervened, though, assigning a flagrant foul 2 to Hamilton for the strike, even though it carried the force of a light slap. The play was initially deemed a flagrant foul 1 but was upgraded upon a video review.
Here's an animated look at the blow.
This is what you would call a strict interpretation by the referees. The NBA rulebook mandates that punches and attempted punches are considered "unsportsmanlike acts" that require automatic ejections. The game officials likely threw the book at Hamilton because his fist was closed and because there was a bit of a wind up motion. While most of us wouldn't consider this a true "punch," it probably is by the letter of the NBA's law, which aims to discourage anything remotely close to truly violent acts.
Hamilton departed with four points (on 2-for-6 shooting) and five rebounds in 16 minutes. J.J. Hickson led the Nuggets with 20 points (on 7-for-13 shooting) and 14 rebounds in a losing effort.
Kevin Durant scored a game-high 30 points (on 11-for-23 shooting) and grabbed six rebounds in 38 minutes for the Thunder. Russell Westbrook added 21 points (on 9-for-16 shooting), 13 rebounds and eight assists.