A logical combination of "tragic" and "travesty". Otherwise known as a false or distorted representation of extreme distress or sorrow.
Shaniqua, yo baby's daddy's death was such a trajesty... that nigga had it comin' when he was out dere fuckin' dem hos day afta day. Bitch had it comin'...
A mix of the words "tasty" and "transient", trastie is used to describe things which are always good but are at some points especially delicious, either literally or figuratively.
That candy is trastie--it is always good but it tastes even better if you eat it and drink Sprite at the same time.