The Collaborative International Dictionary of English v.0.48:

Enterobacteriaceae \En`ter*o*bac`te*ri*a"ce*ae\
   ([e^]n`t[~e]r*[-o]*b[a^]k`t[=e]r*[=e]*[=a]"s[=e]*[=e]), prop.
   n. (Microbiol.)
   a natural family of rod-shaped gram-negative bacteria, most
   of which occur normally or pathogenically in intestines of
   humans and other animals, and some of which grow in plants.
   The type genus is Escherichia. They are aerobic and
   facultatively anaerobic, and may be motile or non-motile.
   Most are easily cultured on artificial growth media. Both
   pathogenic and non-pathogenic strains exist.
   [PJC]

WordNet (r) 3.0 (2006):

Enterobacteriaceae
    n 1: a large family of Gram-negative rod-shaped bacteria of the
         order Eubacteriales [syn: Enterobacteriaceae, family
         Enterobacteriaceae]