naked virus, nonenveloped virus a virus lacking an outer lipoprotein bilayer. neurotropic virus one that has a predilection for and causes infection in nervous tissues, e.g., the rabies virus. Norwalk virus a calicivirus that is a common agent of epidemics of acute gastroenteritis. oncogenic viruses an epidemiologic class of viruses that are acquired by close contact or injection and cause usually persistent infection; they may induce cell transformation and malignancy.
Define stumbling block: an obstacle to progress; an impediment to belief or understanding : perplexity â stumbling block in a sentence an obstacle to progress; an impediment to belief or understanding : perplexityâ¦
Definition of block for Students. 1  1 : a solid piece of some material usually with one or more flat sides a block of ice. 2  2 : an area of land surrounded by four streets in a city. 3  3 : the length of one side of a city block. 4  4 : a number of things thought of as forming a group or unit a block of seats.