What does "krass" mean?
During conversations with native German speakers, I have heard the word "krass" used in different contexts. But I still don't know how to translate it.
"krass" is actually not such a new word as it's modern slang usage suggests. It is a loanword from Latin "crassus".
In general usage "krass" is used for extremes in either a positive or mostly a negative connotation:
Diese Aussage steht in krassem Gegensatz zu seiner sonstigen Einstellung.
Dies war ein besonders krasser Fall von Betrug.
From the 18. Century krass was also used by students, apparently first in the idiom
"Ein krasser Fuchs" - a young student with little experience in life
The Grimms wrote in their dictionary:
KRASS, plump, grob, derb, dann arg, schrecklich, fürchterlich, nach lat. crassus, doch vermengt mit grasz, gräszlich; ein in manchen kreisen beliebtes superlativisches kraftwort, bes. studentisch (krasser fuchs, kerl), seit ende 18. jh.
Only in recent years "krass" is also used in German youth slang with several meanings that have already been pointed out.
An appropriate translation can not be done without a context because of the so many different meanings "krass" can have.
Others do not agree with you on the etymology of "gross": http://www.etymonline.com/index.php?term=gross&allowed_in_frame=0
There is of course also "crass": http://www.etymonline.com/index.php?term=crass&allowed_in_frame=0