Source : Webster's Revised Unabridged Dictionary (1913)

Pollinium \Pol*lin"i*um\, n.; pl. {Pollinia}. [{NL}. See
   {Pollen}.] (Bot.)
   A coherent mass of pollen, as in the milkweed and most
   orchids.

Source : WordNet®

pollinium
     n : a coherent mass of pollen grains (as in orchids)
     [also: {pollinia} (pl)]