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The word "nice" with several appended "e"s includes a degree of "niceness" to the original phrase. It is used in online chats to indicate strength of the usage of the word without using modifiers such as "very" or "quite".
DudeA: "I just finished my homework."
DudeB: "nicee."

In another situation:
DudeA: "I just rooted the NCSA!"
DudeB: "niceeeeeeee!"
by g4pro November 16, 2004
good, fun, amazing, nice looking
that ones a bit nicee
by the teng maker May 30, 2011