Definition of "wharf-rat" [wharf-rat]

• The common brown or Norway rat, Mus decumanus, when living in or about a wharf, considered with reference to its being in many places an imported animal, first naturalized in wharves after leaving the ship which brings it, or to the special size, ferocity, or other distinctive character it acquires under the favorable conditions of environment afforded by wharves, shipping, and storehouses. (noun)
• Hence A fellow who loafs about or haunts wharves, making a living as best he can, without regular or ostensible occupation. (noun)

The Century Dictionary (Public Domain)

• "They sent Helen to college, but they could afford only one semester, and soon she was back in Los Angeles, taking a “business course” (the typical typing and shorthand classes girls of her station were sent to) and then working “like a wharf-rat” at secretarial jobs, supporting everyone."
• "Besides, there were her sister, and Mrs. Hadley, and the young oyster pirate, and the whiskered wharf-rat, all with glasses in their hands."
• "Tess; a Mrs. Hadley, who chaperoned them; "Whisky" Bob, a youthful oyster pirate of sixteen; and "Spider" Healey, a black-whiskered wharf-rat of twenty."