# verb. - enter or gain access to (an organization, place, etc.) surreptitiously and gradually, especially in order to acquire secret information. * the organization has been infiltrated by informers - (of a liquid) permeate (something) by filtration. * virtually no water infiltrates deserts such as the Sahara
# noun. - an infiltrating substance or a number of infiltrating cells. * a chest radiograph revealed a patchy infiltrate in the left lower lobes