A “double doink" refers to a missed field goal attempt where the football hits both the upright goalpost and the crossbar before falling to the ground without going through the uprights, effectively being a double deflection.
In 2000 Chris Berman is believed to be the first person to use the phrase "double doink' when describing a missed field goal by the Detroit Lions’ kicker, Jason Hanson.
One of the most infamous double doinks took place on 1/6/2019 during the 2018 NFC Wild Card game between the Eagles and the Bears. Al Michaels and Cris Collingsworth were calling the game. The Eagles were ahead 16 – 15, and there was less than a minute in the game. The Bears had the ball and were moving downfield. With 11 seconds on the clock, the Bears opted for a game winning 33-yard field goal attempt by Cody Parkey. The ball was kicked and the play by play went like this:
Michaels: “And ... Oh! It hits the upright again! That’s impossible!" Collingsworth: “Did this hit the upright and the crossbar?” (during the replay) “Oh my goodness ... The Bears’ season’s gonna end on a double doink.”
To date there are 4 kickers in the NFL that have achieved the prestigious double doink – Jason Hanson, Harrison Butker, Cody Parkey (which after replay was listed by GSIS as a block), and Will Lutz.