n. [capitalized] A diminutive of the name John.n. In ichthyology, a cottoid fish, Oligocottus maculosus, with a naked skin, slender head narrowed above, and pointed snout. It is a small species, very abundant along the western coast of the United States.n. Among sailors, a kind of penguin, Pygoscelis tæniata.n. The fish Etheostoma nigrum, a kind of darter.n. A hanger-on about a theater.