WordNet (r) 3.0 (2006):
N.B. n 1: a Latin phrase (or its abbreviation) used to indicate that special attention should be paid to something; "the margins of his book were generously supplied with pencilled NBs" [syn: nota bene, NB, N.B.]V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):
NB Nota bene (slang, Usenet, IRC)