WordNet (r) 3.0 (2006):

dubnium
    n 1: a transuranic element [syn: dubnium, Db, hahnium,
         element 105, atomic number 105]

The Elements (07Nov00):

dubnium
Symbol: Db
Competing name for unnilquadium, the 104th element, proposed by the
IUPAC. Finally in 1997 the IUPAC decided to use Dubnium as the official
name
of the 105th element.