Ian Bogost refers to “discrete interlocking units of expressive meaning” as unit operations.
If that sounds confusing, you aren’t alone! It took me a while to wrap my head around this concept. The idea, as I understand it, is that a unit is a bite size piece of our modern culture. Multiple units can “snap together” as it were, to form new and interesting cultural experiences.
A concrete example of this rather abstract theory would be the film “Scott Pilgrim Vs The World”. I say film, but it actually started as a series of books. In either case, the storyline is absolutely packed with references and symbolism from video games such as Tetris and Zelda. So Scott Pilgrim is a unit of culture, which references other units such as the games mentioned. The film referenced the book. And to come full circle, there was a game released the same time as the movie, which itself is done in an extremely retro style that recalls games from the 80’s.
Some examples of the interlocking cultural units/references:
Mario reference on one of the book covers.
Sonic references inside the book.
The Scott Pilgrim game (bottom) evokes the style of 80’s games like River City Ransom (top).