lactobacillus(n = noun.animal) - a Gram-positive rod-shaped bacterium that produces lactic acid (especially in milk);
is a kind of eubacteria, eubacterium, true bacteria
is a member of genus lactobacillus
has particulars: acidophilus, lactobacillus acidophilus
lactobacillus, n. (pl. -bacilli) Biol. any Gram-positive rod-shaped bacterium of the genus Lactobacillus, producing lactic acid from the fermentation of carbohydrates.