It basically means
sex, or, in most of the cases, it means "as good as sex" (i.e. the highest point of pleasure .. or .. the best of the best). It's a one word answer.
Synonym for :
sex,
fuckawesome,
orgasmic,
mindblowingPronunciation - emphasis on the "kh" ( "from the epiglottis" ; :phlegm: ). This word is strictly used by engineering students, or basically 20-year-old-Indian-bachelors-who-are-desperate-to-get-
laid.
Some people also have the tendency to shorten the word to just "Sakkhh".