sensi is just an abbreviation for sensemillia, "seedless". It just means that the plant that produced the herb was a female that didn't get pollinated, and therefore didn't produce seeds. It is a general term that is oft-misused to mean that the herb is the chronic, whih it very well could be. But basing your decision on buying shouldn't hinge on it being sensi, for 50 bones, I'd want to see it first and make sure it was dank as well as sensi.