look up any word, like donkey punch:
 
1.
addictive, or not quite fully addictive. Sometimes a euphemism for the word "addictive".

Citation: Harper's Magazine, September 2005, p. 17, "Do Not Pass Out."
Chocolate truffles may not be addictive, but they sure are moreish.
by some guy from Albuquerque September 02, 2005
 
2.
Chiefly British slang meaning tasty or appetising.
Michael Moore finds cheeseburgers very moreish.
by Rule 14 July 16, 2004
 
3.
Addictive, describing a strong addictive nature. But also enjoyable.
Superhans "havin a nice relaxing smoke of crack"
after getting very high..
Superhans "Tell ya what, that crack is really moreish"
by some guy 182 October 06, 2009