n.
Pronunciation: ' äp-s ə -n ə n
Function: noun
Etymology: Latin opsonare to buy provisions, cater (fr. Greek ops ō nein ) + English 1 -in ― more at OLIGOPSONY
Date: 1903
: any of various proteins (as antibodies or complement) that bind to foreign particles and cells (as bacteria) making them more susceptible to the action of phagocytes