bac·te·roi·des \ˌbaktəˈrȯi(ˌ)dēz\noun Etymology: New Latin, from bacterium + -oides 1.capitalized: a genus (the type of the family Bacteroidaceae) of gram-negative anaerobic bacteria having rounded ends, producing no endospores and no pigment, and living usually in the normal intestinal tract 2.pluralbacteroides: a bacterium of Bacteroides or a closely related genus