A woman wearing only a t-shirt that stops above her waist (in lieu of committing to complete nudity). It occasionally means that there is some aspect of her breast appearance (i.e. size, nipple shape, etc.) that she's embarrassed about, but more often suggests that she's just trashy and has poor taste.
"Honey, did you lose Barbie's pants again? That little doll of yours is always shirtcreasing."
"That shirtcreasing dreadlocks girl grosses me out. I feel like if I even get near her herpes might make an airborne jump."