tri
Explanation
This comic is a single-panel joke about a person in a polyamorous ("poly") trio who wants to break up with both partners simultaneously — not for emotional reasons, but purely for the wordplay opportunity.
The character in the center tells their two partners: "Listen. I love you both. You love me. We're wonderful together. But if we agree to break up all at the same time, we can tell people 'I was married, but got trivorced.'"
The caption reads: "This is why I would never last in a poly trio."
The entire joke is that the character is willing to destroy a perfectly functional three-way relationship solely for the sake of coining the portmanteau "trivorced" (tri + divorced). The humor lies in the absurd prioritization of a pun over genuine human relationships. The caption, written from Weinersmith's perspective, suggests that his compulsive need to make wordplay jokes would sabotage any polyamorous arrangement — not because of jealousy or communication difficulties (the usual reasons poly relationships fail), but because the linguistic possibilities would be too tempting to resist. It's a self-deprecating joke about being the kind of person who would burn down their love life for a good bit.