noun
: something (as a geographical, ecological, physiological, anatomical, or psychological barrier) that limits interbreeding between groups and is thereby a major factor in the differentiation of biologic units (as races or species)
noun
: something (as a geographical, ecological, physiological, anatomical, or psychological barrier) that limits interbreeding between groups and is thereby a major factor in the differentiation of biologic units (as races or species)
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012