Definition of "dozen"

dozen

/ˈdʌzən/

noun
plural dozens or dozen
1. A set of twelve.
2. (as plural only, always followed by of) A large, unspecified number of, comfortably estimated in small multiples of twelve, thus generally implied to be significantly more than ten or twelve, but less than perhaps one or two hundred; many.
  Quotations
  Although there are dozens of different types of gems, among the best known and most important are diamond, ruby and sapphire, emerald and other gem forms of the mineral beryl, chrysoberyl, tanzanite, tsavorite, topaz and jade.
  2012 March, Lee A. Groat, “Gemstones”, in American Scientist‎, volume 100, number 2, archived from the original on 14 June 2012, page 128
3. (metallurgy) An old English measure of ore containing 12 hundredweight.
  Quotations
  The dozen as a measure for iron ore remained almost completely constant at 12 cwts. during the sixteenth and seventeenth centuries.
  1957, H.R. Schubert, History of the British Iron and Steel Industry, page 139
4. (bingo) The number twelve.