Pretty much what is says on the tin. Inspired by the "unwanted_erection" tag on other sites I tried to collect some examples but you run into the issue of "is this character just flustered or is the erection causing distress" so perhaps it would be "embarrassing" or shy rather than unwanted but I prefer unwanted because it's a specific scenario. So so far I've included cases where the erection could be considered unwanted like when wrestling post #7228680 post #5247954, being in public post #4802315 or someone hiding an erection while the "main" character does something sexual in the foreground post #7156681. favgroup #32347
Different from hiding erection as it still includes stuff like post #4102170 post #4956214 where the character is distressed but not actively hiding it.
Updated